Chapter 05Calendar · Know-how
Which climate region am I in?
Look up your county in the DOE Building America county list. It runs state by state, then county by county, and the region boundaries follow county lines, so your county's row gives one answer. There are eight regions: hot-humid, hot-dry, mixed-humid, mixed-dry, marine, cold, very cold and subarctic. Two lines set most of them apart: whether any winter month averages below 45 F, and how many heating degree days the place gets in a year.
Source: DOE Building America climate regions by county, checked October 13, 2026.
- Building America climate regions in the U.S.8 DOE Building America climate regions by county, October 13, 2026
- The winter monthly average that splits hot from mixed45 F DOE Building America climate regions by county, October 13, 2026
- Heating degree days a year where cold begins5,400 DOE Building America climate regions by county, October 13, 2026
The eight regions in plain words
- Hot-humid: more than 20 inches of rain a year and long stretches of muggy heat in the warm half of the year.
- Hot-dry: less than 20 inches of rain a year, and every month averages above 45 F.
- Mixed-humid: more than 20 inches of rain, about 5,400 heating degree days or fewer, and at least one winter month that averages below 45 F.
- Mixed-dry: the same winter as mixed-humid, with less than 20 inches of rain.
- Cold: 5,400 to 9,000 heating degree days a year.
- Very cold: 9,000 to 12,600 heating degree days.
- Subarctic: 12,600 heating degree days or more. In the U.S. that's only parts of Alaska.
- Marine: the coldest month averages between 27 F and 65 F, the warmest under 72 F, and summers are dry.
Source: DOE Building America climate regions by county, checked October 13, 2026.
Find your county in the list
The DOE guide ends with a table of every U.S. county. Region lines follow county boundaries, so you don't need a map or a ZIP code lookup. You need your county's name.
Source: DOE Building America climate regions by county, checked October 13, 2026.
Know your county
It's on your property tax bill, your voter card or the county government's website. Cities can sit in more than one county, so check the address itself.
Open the county list
The PDF is linked in the sources below. The table starts after the region definitions and runs state by state, then county by county, A to Z.
Read the Building America column
That word (Cold, Hot-Humid, Marine and so on) is your region. It's the one to pick in the home maintenance calendar.
Write the IECC number down too
The table also gives an IECC zone number (1 to 8) and a letter. Builders and code offices use that one. Keep both on the first page of your house binder.
Source: DOE Building America climate regions by county, checked October 13, 2026.
Some counties, for a feel of the map
- Miami-Dade County, Florida, and Harris County, Texas (Houston): hot-humid.
- Maricopa County, Arizona (Phoenix), Clark County, Nevada (Las Vegas), and Los Angeles County: hot-dry.
- Wake County, North Carolina, Fairfax County, Virginia, and New York County, New York: mixed-humid.
- Bernalillo County, New Mexico (Albuquerque): mixed-dry.
- King County, Washington (Seattle), Multnomah County, Oregon (Portland), and San Francisco: marine.
- Cook County, Illinois (Chicago), Denver, and Hennepin County, Minnesota (Minneapolis): cold.
- Cook County, Minnesota, and Anchorage, Alaska: very cold.
- North Slope Borough, Alaska: subarctic.
Source: DOE Building America climate regions by county, checked October 13, 2026.
Two counties with the same name
Cook County, Illinois, is cold. Cook County, Minnesota, is very cold. Always read the state column before the county.
Source: DOE Building America climate regions by county, checked October 13, 2026.
What heating degree days mean
A heating degree day measures how far a day's average temperature falls below 65 F. The DOE guide's own example: if a day averages 35 F, that day counts as 30 heating degree days, because 65 minus 35 is 30. Add up every day in a year and you get the yearly number. More degree days means a longer, colder heating season.
Source: DOE Building America climate regions by county, checked October 13, 2026.
The 45 F line works differently. It asks whether the average for any winter month drops below 45 F. Hot-humid and hot-dry places stay above it all year. Mixed regions dip below it in winter, but stay at or under about 5,400 heating degree days.
Source: DOE Building America climate regions by county, checked October 13, 2026.
Let the tool do the arithmeticHome maintenance calendarPick your region in the home maintenance calendar. It turns on the before-the-freeze jobs by default in mixed, marine and colder regions, and lays out a dated year from your start month.Example: 8 dated jobs a year (Cold region, plus 2 monthly checks)Open the toolWhat the region does on your calendar
In the calendar, the region decides one thing: whether the freeze rows (hoses off, outdoor faucets drained, winter supplies) start switched on. Your own first-freeze month wins over the region. If you know frost usually comes in late October where you live, enter that and the hose job moves to the month before.
A planning label, nothing more
The region is a broad label for planning a year of household jobs. It doesn't tell you what equipment, insulation or windows a house needs. Those questions go to a contractor or your local building department.
Checklist to print
Do this once per home:
- Find the county on a tax bill or voter card
- Open the DOE county list (PDF)
- Find the state heading first
- Find the county row under it
- Write down the Building America region
- Write down the IECC zone number and letter
- Note the usual first-freeze month, if known
- Pick the region in the maintenance calendar
- Put both on the binder's first page
Tips and tricks
- Tip 01
Read the state first
Several states share county names, and they don't always share a region. Find the state heading, then the county.
- Tip 02
Near a region line? Trust your own winters
Counties next to each other can sit in different regions. If your county is listed as mixed but frost comes every October, enter October as the first-freeze month in the calendar.
- Tip 03
Keep the two names apart
The Building America name (Cold, Marine and so on) and the IECC zone number describe the same place in two ways. The calendar uses the name. Builders and code offices use the number.
Source: DOE Building America climate regions by county, checked October 13, 2026.
- Tip 04
Look it up once
A county's region doesn't change from year to year. Write it on the year sheet and in the binder, and you won't have to look again until you move.
What we would do
Five minutes with the county list, then set up the calendar
Open the DOE county list, find your state and county, and write down the Building America name and the IECC number. Pick that region in the home maintenance calendar, add your first-freeze month if you know it, and print the year sheet.
Questions
What climate zone am I in?
Find your county in the DOE Building America county list. Each county gets one of eight regions: hot-humid, hot-dry, mixed-humid, mixed-dry, marine, cold, very cold or subarctic.
Source: DOE Building America climate regions by county, checked October 13, 2026.
Is the Building America region the same as the IECC climate zone?
They describe the same places in two ways. Building America groups the IECC zones into eight named regions. Cold, for example, covers IECC zones 5 and 6, and marine covers the counties with a C moisture letter.
Source: DOE Building America climate regions by county, checked October 13, 2026.
What is a heating degree day?
It counts how far a day's average temperature falls below 65 F. A day that averages 35 F counts as 30. A year's total tells you how long and cold the heating season is.
Source: DOE Building America climate regions by county, checked October 13, 2026.
Is this the same as the USDA plant hardiness zone?
No. Hardiness zones are for gardening. The DOE regions are for buildings and are set by county, so look up the DOE list for the house.
Which regions get the freeze jobs in the calendar?
Mixed-humid, mixed-dry, marine, cold, very cold and subarctic start with the before-the-freeze rows on. Hot-humid and hot-dry start with them off. Your own first-freeze month overrides either way.
Source: DOE Building America climate regions by county, checked October 13, 2026.
Part of a system
This page is one part of a bigger job. The system page puts the parts in order.
The tool and more guides
Chapter 05Home maintenance calendarPick your climate region, say whether you own or rent and tick what the house has. Get a year of household jobs by month and a year sheet to print.Open the tool
Practical noteBooking the cooling check-up: what to have ready before you callBook the spring AC check-up with the system's model, its service history and the rooms that run hot in front of you. Then write the date down.Read the guide
Know-howHow much water to store, and where it fitsOne gallon a person a day: 56 gallons for four people over two weeks, 12 in the go-bag. Where to keep it, and the dates to write on it.Read the guide- Chapter 05All calendar toolsA home maintenance calendar for your climate region: the jobs to book, check and write down each month, for owners and renters, with a year sheet to print.Open the chapter
Sources
- Guide to Determining Climate Regions by County (Building America Best Practices Series, Volume 7.3, PNNL-17211 Rev. 3), U.S. Department of Energy, Building America (Pacific Northwest National Laboratory). Checked October 13, 2026.
Every outside number on this page names its source and the date we checked it. See them all on the sources page. Spotted an error? Tell us.