NOAA climate normals for 3,107 counties. See which half of the year drives your energy bill.
3,208 / 1,605heating / cooling degree days, Mecklenburg County, NCNOAA NCEI county normals, 1991-2020, base 65°F. 67% of this county’s degree days are heating.
The short answer
Degree days measure how much heating or cooling a climate asks for in a year. Pick your county to get both figures, base 65°F, from NOAA’s 1991-2020 normals.
Mecklenburg County, NC logs 3,208 heating and 1,605 cooling degree days, so 67% of its demand is heating. Use it to rank climates. It does not size equipment.
Pick your county
NOAA’s 1991-2020 normals for 3,107 counties, base 65°F. Nothing leaves your browser.
—Annual degree days, base 65°F
—Heating / cooling split
—Which rating matters most
—Distance from the comparison
—Total demand, nationally
What this assumed
—
A lookup in NOAA’s public county normals, plus simple math. Degree days rank seasonal demand. They carry no humidity and do not size equipment; that takes an ACCA Manual J. HyreHVAC does not sell, install or service equipment.
How do you read heating and cooling degree days?
Look at two things: how big each number is, and how they split. One number covers the cold half of the year, the other the warm half.
A heating degree day is one degree of daily average temperature below 65°F. A day averaging 45°F adds 20. A cooling degree day is the same above 65°F. This tool reports the yearly totals, averaged over 1991-2020.
The size shows how much heating or cooling the climate asks for. Lake County, CO tops the heating list at 10,968. Orange County, CA has the lowest combined total in the country, 2,626: a climate that barely needs heating or cooling.
The split shows which half of the year drives your bill, and it is the more useful number. At 90% heating, the furnace or heat pump heating rating (AFUE or HSPF2) decides the bill. At 30% heating, SEER2 does.
HyreHVAC calculation: 409 of the 3,107 counties log more cooling than heating degree days. 474 sit in the mixed band, 40% to 60% heating, where both ratings matter and one heat pump doing both jobs makes the strongest case.
The distance from your state is the third output, and it is our math, not NOAA’s. It shows whether the state-level figure you see elsewhere ever described your county.
How do you use the degree-day lookup?
1
Pick your county
Use the county the house sits in, not your mailing city. They differ more often than you would think at metro edges. It is on your property tax bill. Comparing two houses? Run both.
2
Choose what to compare against
Your state’s county mean is the default: it shows whether a state figure would have misled you. The national county mean places you against the country. The full range in your state shows your state’s coldest and warmest counties.
Nothing here is estimated. Both figures are a lookup in a public federal dataset, and the comparison is simple math.
How does the degree-day lookup calculate its results?
Annual HDD65
The sum of the county’s twelve published monthly heating degree-day normals for 1991-2020, rounded to a whole degree day. Nothing else is done to it.
Annual CDD65
The same, for the cooling series (element 26).
Heating share
HDD ÷ (HDD + CDD) × 100. Above 50% is heating-dominated, below is cooling-dominated. HyreHVAC calculation.
State county mean
Σ county HDD ÷ number of counties in the state, and the same for CDD. Every county counts once. HyreHVAC calculation, not NOAA’s area-weighted statewide normal.
Distance from the state
(county − state county mean) ÷ state county mean × 100, for heating and cooling separately. HyreHVAC calculation.
National percentile
The county’s rank by total degree days (HDD + CDD) among all 3,107 counties. HyreHVAC calculation.
That is the whole method. No model, no fitting, no weighting.
What do degree days look like across the US?
County
HDD65 / CDD65
Split
National percentile
Against its own state
Monroe County, FL
178 HDD65 · 4,460 CDD65
Cooling-dominated: 4% heating
16th percentile
−82% HDD, +41% CDD vs the FL county mean (1,004 / 3,166, 67 counties)
Miami-Dade County, FL
185 HDD65 · 4,312 CDD65
Cooling-dominated: 4% heating
11th percentile
−82% HDD, +36% CDD vs the FL county mean (1,004 / 3,166, 67 counties)
Harris County, TX
1,309 HDD65 · 3,089 CDD65
Cooling-dominated: 30% heating
9th percentile
−42% HDD, +21% CDD vs the TX county mean (2,248 / 2,551, 254 counties)
Clark County, NV
2,611 HDD65 · 2,637 CDD65
Balanced: 50% heating
34th percentile
−55% HDD, +261% CDD vs the NV county mean (5,792 / 731, 17 counties)
Mecklenburg County, NC
3,208 HDD65 · 1,605 CDD65
Heating-dominated: 67% heating
22nd percentile
−8% HDD, +16% CDD vs the NC county mean (3,496 / 1,387, 100 counties)
New York County, NY
4,700 HDD65 · 1,121 CDD65
Heating-dominated: 81% heating
48th percentile
−31% HDD, +139% CDD vs the NY county mean (6,821 / 469, 62 counties)
King County, WA
6,290 HDD65 · 80 CDD65
Heating-dominated: 99% heating
59th percentile
−1% HDD, −67% CDD vs the WA county mean (6,331 / 239, 39 counties)
Modoc County, CA
6,745 HDD65 · 267 CDD65
Heating-dominated: 96% heating
71st percentile
+89% HDD, −72% CDD vs the CA county mean (3,568 / 969, 58 counties)
Hennepin County, MN
7,861 HDD65 · 662 CDD65
Heating-dominated: 92% heating
90th percentile
−8% HDD, +29% CDD vs the MN county mean (8,516 / 515, 87 counties)
Lake County, CO
10,968 HDD65 · 0 CDD65
Heating-dominated: 100% heating
99th percentile
+46% HDD, −100% CDD vs the CO county mean (7,494 / 381, 64 counties)
Each row is the calculator’s own output for that county. Read top to bottom, it tours the range of US climates.
Two rows stand out. Clark County, Nevada is almost exactly balanced, yet sits 261% above the Nevada mean on cooling, because the other 16 Nevada counties are high desert. Lake County, Colorado records zero cooling degree days: a measured zero at 10,000 feet.
How does the comparison setting change the answer?
The tool has two inputs, and only the comparison is a choice. With the county held at Mecklenburg County, NC, the three settings give, word for word from the engine:
Against my state’s county mean: “−8% HDD and +16% CDD against the NC county mean (3,496 / 1,387, 100 counties).”
Against the national county mean: “−35% HDD and +27% CDD against the mean of all 3,107 counties (4,914 / 1,268).”
The full range in my state: “counties in NC run 2,441 to 5,627 HDD and 272 to 1,933 CDD. Yours is 3,208 / 1,605.”
HyreHVAC analysis: all three are correct. Against North Carolina the county is typical. Against the country it is mild and warm. Within its own state it sits in the lower third for heating.
The right comparison depends on your question. The default answers the first one most people have: does a state-level figure apply to me?
What changes the degree-day answer?
1stWhich county you pick: This is a lookup. The county is the answer, and no other input can fix a wrong onePick the county the house is in, not the mailing city
62×Geography: The gap between the lowest and highest county heating figure in the countryMonroe County, FL at 178 HDD to Lake County, CO at 10,968 HDD
402Counties more than 25% from their state mean: How far off a state-level tool would be for themHyreHVAC calculation
NoneNot included: your house. Insulation, air leaks, windows and orientation change the load a lot and these figures not at allThat is what Manual J: Residential Load Calculation, 8th edition is for
NoneNot included: humidity. Degree days are temperature only. In the Gulf states, moisture often decides the equipmentNot in the source data at any level
NoneNot included: fuel price. Degree days rank demand, not cost. Two counties with the same figures can have very different billsSee electricity against gas, by state
What mistakes do people make with degree days?
Sizing equipment from a degree-day total
A yearly energy index cannot give a capacity. Size comes from ANSI/ACCA 2 Manual J - 2016 on your house. If degree days appear in a sizing justification, the sizing was not done. See the AC sizing calculator for the same point.
Reading a low heating figure as “no heating needed”
A mild-winter county still has cold mornings, and equipment is chosen for those. Degree days give the season’s total. The worst morning of the year is what the design temperature covers.
Comparing figures on different bases
Figures on base 60, 55 or 50 are also published, and a base-50 heating figure is much smaller for the same climate. Check the base before comparing sources. Everything here is base 65.
Comparing a normal to a single year
A 1991-2020 normal is an average. Utilities often publish actual degree days for one year, which will not match. Both are right; they answer different questions.
Assuming the state efficiency region matches your climate
Federal regional standards follow state lines. Every county in a state gets the same rule, even where counties differ eightfold. The legal minimum and the right choice are separate questions.
Treating a missing county as a zero
Alaska, Hawaii, DC and the territories are not in the NOAA county series. That is a gap in the data. A zero that does appear, as in several Colorado counties, is a real measurement.
Using the split to pick a fuel
The split tells you which rating to check. It does not say whether a heat pump or furnace is cheaper to run. That depends on your electricity and gas prices, which vary more between states than climate does.
Why is a state average misleading?
Because the counties inside most states do not look alike. Most HVAC calculators ask for your state or one of five climate zones. Here is what that costs you.
The twelve states with the widest county range: each line runs from the state’s lowest-HDD county to its highest; the figure at the right is the ratio between them.HyreHVAC calculation from NOAA NCEI nClimDiv county degree-day normals, 1991-2020, retrieved 2026-09-05.
HyreHVAC calculation: of the 3,107 counties NOAA covers, 1,427 (45.9%) sit more than 10% from their state’s county mean for heating. 402 (12.9%) sit more than 25% away, and 106 (3.4%) more than 50%.
Cooling varies even more: 921 counties (29.6%) are more than 25% from their state’s county mean.
HyreHVAC calculation: California is the extreme. Its counties run from 952 heating degree days in Imperial County to 7,591 in the northeast, 8.0 times as many.
Texas runs 558 to 4,599 across 254 counties. Florida, often treated as one climate, runs 178 to 1,764: a ratio of 9.9, the widest in the country.
HyreHVAC analysis: in the big states, where most people live, the state average describes no real place. A Californian gets the midpoint of a range from desert to alpine. The error is largest exactly where the population is.
A state figure is fine in small, flat states. Rhode Island’s counties span 480 degree days, 8% of its mean. Delaware’s span 11%. There, this tool will simply confirm the state number.
In which states is a state figure safe?
County spread in heating degree days, by state: range from lowest to highest county, as a percentage of the state’s simple county mean.HyreHVAC calculation from NOAA nClimDiv county normals, 1991-2020.
HyreHVAC calculation: the map shades each state by how wide its county heating range is, as a share of the state mean. 20% means the coldest and warmest counties differ by a fifth of the average. 180% means they differ by nearly twice it.
HyreHVAC analysis: the pattern follows mountains and coastline, not latitude. Mild-winter states score worst, because a coastal county and a high inland one share a border.
North Dakota is cold everywhere and has one of the narrowest ranges, 20%. A state figure is roughly right for every county there.
What to do: find your state on the map. If it is dark, treat any climate figure that is not for your county as a placeholder.
How far are well-known counties from their state average?
Selected counties against their own state’s county mean, heating degree days. Positive means colder than the state’s typical county.HyreHVAC calculation on NOAA nClimDiv county normals, 1991-2020.
HyreHVAC calculation: this chart draws the calculator’s third output for nine counties. Each bar is the county’s heating degree days against the simple mean of the counties in its state.
HyreHVAC analysis: two bars are the same state. Imperial County sits far below the California mean and Modoc County far above it. One state figure is wrong for both, in opposite directions.
Now look at King County, Washington. Its heating figure is within a point or two of the state mean, so a state figure works for heating. Its cooling figure is a small fraction of the state mean.
A tool that gets one of the two numbers right has not got your climate right. That is why the calculator reports the distance for both.
What can degree days tell you, and what can they not?
The question
Do degree days answer it?
What does answer it
Which half of the year costs me more
Yes: that is what the split of the two figures shows
The heating/cooling split this tool reports, then your own fuel prices
Should I check the heating or cooling rating of a heat pump first
Yes, as a first cut: a 90% heating county is decided by HSPF2, not SEER2
No: degree days measure a season’s energy, not capacity
ANSI/ACCA 2 Manual J - 2016, a room-by-room load calculation on your house
What outdoor temperature must my equipment still work at
No: a yearly total says nothing about the coldest hour
The ASHRAE 99% or 99.6% winter design temperature for your location, used in Manual J
How much moisture removal do I need
No: degree days contain no humidity at all
The latent (moisture) load from a Manual J that counts air leaks and indoor moisture
Do I need a cold-climate heat pump
Partly: the heating share shows how much of the year depends on it
The unit’s rated low-temperature performance. ENERGY STAR’s cold-climate criterion is a COP of 1.75 and 70% of the 47°F heating capacity at 5°F
Which efficiency minimum applies to my install
No: federal regions follow state lines, not degree days
10 CFR 430.32. See the regional standards section below
Degree days rank climates by how much heating or cooling a season needs. They do not describe a house.
Do federal efficiency rules follow your climate?
No. They follow state lines. This is the one place a state-level climate judgment is legally binding.
Under 10 CFR 430.32(c)(5) and (c)(6), split-system air conditioners installed on or after January 1, 2023 in the Southeast or Southwest must meet a higher minimum than the national one. In those regions the rule applies at installation, not manufacture.
The Southwest is Arizona, California, Nevada and New Mexico. The Southeast is Alabama, Arkansas, Delaware, Florida, Georgia, Hawaii, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, Puerto Rico, South Carolina, Tennessee, Texas, Virginia, the District of Columbia and the US territories.
HyreHVAC calculation: California is one Southwest state. Its counties run from 952 to 7,591 heating degree days and 85 to 4,359 cooling degree days. Arizona runs 1,148 to 5,586 heating degree days across just 15 counties.
HyreHVAC analysis: an enforceable rule needs a fixed boundary, so state lines make sense for regulation. But the rule only sets the legal floor. In a state with that much climate range, it cannot tell you which rating will matter to you.
What to do: use the region to check the equipment is legal. Use your county’s two numbers to decide which rating to focus on. Mixing them up is how people pay for the wrong half of a machine.
What does this lookup not know?
It knows temperature and nothing else
A degree day is air temperature against a 65°F base, over time. No humidity, sun, wind or cloud. In the Gulf states, moisture often decides the equipment, and neither number shows it.
The 65°F base is a convention, not your thermostat
It assumes a house needs heat below 65°F outdoors. A tight new house needs heat at a lower temperature, a leaky old one at a higher one. NOAA publishes base 65, so use these to rank climates, not predict run hours.
A county is not a microclimate
County values come from station data across the county. A county with big elevation changes averages them away. Still far better than a state figure.
Normals describe the last 30 years, not next year
The 1991-2020 normal is the current standard period. A period ending in 2030 will read differently, and any single year can differ a lot.
It does not size or choose equipment
Capacity comes from Manual J: Residential Load Calculation, 8th edition, and equipment choice from Manual S: Residential Equipment Selection. Neither uses a yearly degree-day total. A contractor who sizes from degree days has skipped the work.
It is not an instruction to touch anything
Gas, refrigerant and electrical work is licensed work. This page helps you read a proposal and ask better questions, not do any part of the job.
What it does know, it knows precisely
Two numbers per county, for 3,107 counties, from a public federal dataset, summed from the published monthly normals and otherwise untouched.
Where do these degree-day figures come from?
Both figures for every county come from NOAA’s National Centers for Environmental Information, nClimDiv county normals: climdiv-norm-hddccy-v1.0.0-20260806 for heating and climdiv-norm-cddccy-v1.0.0-20260806 for cooling.
Both files are dated 2026-08-06 and were retrieved 2026-09-05. They are a US Government work in the public domain.
HyreHVAC calculation: the source holds twelve monthly values for each of twelve normal periods. We used period 0010, 1991-2020, and summed its twelve months to a yearly figure. Nothing was smoothed, re-based or weighted. Names come from the Census 2024 county gazetteer.
HyreHVAC calculation: the state mean is ours, not NOAA’s: a simple average in which every county counts once. NOAA’s area-weighted statewide normal is a different number, and we do not use it.
Nine county records did not match the 2024 gazetteer by code, so we supplied names. They are Connecticut’s eight old counties, which the Census replaced with nine planning regions after 2022, and Baltimore City (511 in NOAA, 510 in FIPS). No value was changed.
Alaska, Hawaii, DC and the territories are missing because the NOAA county series does not cover them. That is a gap in the data, not a low reading.
HyreHVAC does not install, service or sell HVAC equipment, and holds no data on quotes, invoices or finished jobs. Nothing here is a price we observed. That is also why these tools can tell you to keep the system you have.
One degree Fahrenheit below 65°F for one day. A day averaging 45°F adds 20 heating degree days. A day averaging 66°F adds none. The yearly total shows how much heating a climate needs. Cooling degree days work the same way above 65°F.
Why use 65°F as the base?
It is the standard convention. It assumes a house needs no heat above about 65°F outdoors, because lights, appliances and people supply the rest. Your house may differ, so treat these figures as a ranking of climates, not a forecast of run hours.
Why county instead of state or ZIP code?
County is the finest level NOAA publishes this series at. 1,427 of the 3,107 counties differ from their state’s county mean by more than 10%, and 106 by more than 50%. It is still not a reading at your address.
Can I size my system from degree days?
No. Size comes from ANSI/ACCA 2 Manual J - 2016, a room-by-room load calculation on your house and its local design temperature. A yearly degree-day total is not an input. A contractor who sizes from degree days or floor area alone has skipped that work.
Does a heating-dominated county rule out a heat pump?
No. It tells you which rating matters most: HSPF2 and low-temperature capacity. ENERGY STAR’s cold-climate criterion asks for a COP of 1.75 and 70% of the 47°F heating capacity at 5°F. Whether it costs less to run than a furnace depends on your fuel prices.
Why is my county’s cooling figure zero?
Because some counties truly record no cooling degree days in the normal period. High-altitude Colorado counties are the clearest cases. A zero is a measured zero. Alaska, Hawaii, DC and the territories are simply not in the dataset.
Are these figures a forecast?
No. A normal is a 30-year average of the recent past, 1991-2020 here. Any single year will differ, sometimes a lot. Use it to compare climates, not to budget one winter.
Does this tell me which efficiency standard applies to me?
No. Federal regional standards for split-system air conditioners are set by state, not by degree days. Every county in a state gets the same rule. Use the region to check the equipment is legal, and your county figures to decide which rating matters.
Do degree days include humidity?
No. They measure air temperature against a fixed base and nothing else. In the Gulf and South Atlantic states, moisture often decides the cooling equipment, and neither number shows it. A high cooling figure says cooling matters, not what kind.
Is the state comparison NOAA’s number?
No. It is our own simple average of the counties in your state, labeled as ours. NOAA publishes an area-weighted statewide figure in a separate file. We count every county once, because the question is how far you sit from a typical county near you.
nClimDiv normals readme: definition of the normal-period codes (NOAA National Centers for Environmental Information, retrieved 2026-09-05. Defines the period codes: 0001 is 1901-1930 through 0010 for 1991-2020. This is how we know which record is the current normal.)
nClimDiv county readme: element codes and state numbering (NOAA National Centers for Environmental Information, retrieved 2026-09-05. Element 25 is heating and 26 is cooling degree days. The state number is alphabetical (01 Alabama), not the FIPS code.)
2024 Gazetteer Files: Counties (national) (US Census Bureau, retrieved 2026-09-05. County and state names, joined by GEOID. Nine NOAA records (Connecticut’s eight legacy counties and Baltimore City) carry names we supplied.)
Air-source heat pumps key product criteria (ENERGY STAR, retrieved 2026-09-05. The cold-climate criterion: a COP of 1.75 and 70% of the 47°F heating capacity at 5°F. No version or effective date was stated.)
Manual J: Residential Load Calculation (Air Conditioning Contractors of America, retrieved 2026-09-05. The method that sizes equipment. It does not use a yearly degree-day total.)