Photo: Boereck 14:52, 27 July 2006 (UTC) · CC BY-SA 3.0Clayton’s winters are milder and less snowy than most of the U.S.
A typical July afternoon reaches 87°, a January night drops to 40°, and snow is almost unheard of.
A year in Clayton at a glance
Each month’s typical high and low, and what it brings.
What stands out about Clayton’s climate
Compared with towns across the U.S., with Clayton’s place in California beside it.
What a year in Clayton feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
A freeze most winters
Frost and day counts come from NOAA’s station at Antioch Pumping Plt #3, CA, 10 miles from the town’s center, 480 ft lower.
The 2023 USDA map puts Clayton’s center in zone 9b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 27°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 19 inches of rain a year
January is the wettest month and July the driest. Rain falls on about 56 days a year. Snow is rare: about 0.0" in a normal year at Concord Wwtp, CA, so most winters see none.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Clayton
62% of the work is heating. Months averaging under 55° run from November through March.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Antioch Pumping Plt #3, CA.
Living with Clayton’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
Zone 9b. Frost comes about 8 winters in 10, so tender plants can often stay out through winter.
Months with highs of 62–84° and lows of 40° or more: March, April, May, June, October and November. 13 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Clayton from natural hazards, river flooding is the largest share (72%); heat waves, cold waves, winter storms and ice storms together are 1%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Clayton and its neighbors
Every town next door is within a degree of Clayton in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Clayton’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Clayton, CA | 40° | 87° | 19" | 0.0" |
| Sierra Vista Southeast, AZ | 32° | 91° | 15" | 0.7" |
| Green, OR | 37° | 86° | 32" | 0.0" |
| Alpine, TX | 30° | 90° | 15" | 2.2" |
| College Place, WA | 30° | 91° | 15" | 7.2" |
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Clayton averaged 1.6° warmer than the 1900s. The biggest change is in January (+2.1°).
A bigger shift than in 63% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Clayton compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Clayton’s place among California’s.
Clayton weather by month
Highs, lows and precipitation from NOAA’s grid at Clayton’s center; snow, wet days and snow on the ground from Concord Wwtp, CA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 55° | 40° | 4.0" | 0.0" | 10 | 0 | 44° – 55° |
| February | 60° | 42° | 3.5" | 0.0" | 10 | 0 | 45° – 57° |
| March | 64° | 45° | 2.9" | 0.0" | 8 | 0 | 48° – 61° |
| April | 69° | 47° | 1.3" | 0.0" | 5 | 0 | 53° – 62° |
| May | 75° | 51° | 0.6" | 0.0" | 3 | 0 | 56° – 71° |
| June | 82° | 56° | 0.1" | 0.0" | 1 | 0 | 64° – 72° |
| July | 87° | 59° | 0.0" | 0.0" | 0 | 0 | 69° – 78° |
| August | 87° | 59° | 0.0" | 0.0" | 0 | 0 | 69° – 78° |
| September | 85° | 57° | 0.1" | 0.0" | 1 | 0 | 67° – 75° |
| October | 76° | 52° | 0.9" | 0.0" | 3 | 0 | 60° – 71° |
| November | 64° | 45° | 2.0" | 0.0" | 6 | 0 | 48° – 59° |
| December | 55° | 40° | 3.8" | 0.0" | 9 | 0 | 44° – 51° |
| Year | 72° | 49° | 19.1" | 0.0" | 56 | 0 |
How much a month can swing
A normal is an average. May swings the most: from 1991 to 2020 its average ranged from 56° to 71°. December is the most reliable, staying within 7°.
Where Clayton’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Clayton’s center.
- Snow: Concord Wwtp, CA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Antioch Pumping Plt #3, CA, 10 miles from the town’s center, 480 ft lower; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Clayton’s climate
What is the weather like in Clayton?
A typical July afternoon reaches 87°, a January night drops to 40°, and snow is almost unheard of. Milder January nights than 89% of U.S. towns; hotter July afternoons than 63% of U.S. towns.
How cold does it get in Clayton in winter?
December nights average 40°. About 7 nights a year reach 32° or below. In the coldest December of the last 30 years the month averaged 44°.
How much snow does Clayton get?
About 0.0 inches in a normal winter at Concord Wwtp, CA, so most winters see none.
How hot does it get in Clayton?
July, with a typical high of 87° and a low of 59°. About 64 days a year reach 90° and 10 reach 100° (Antioch Pumping Plt #3, CA).
When is the first and last frost in Clayton?
There is no reliable frost date: a 32° night comes in about 81% of winters at Antioch Pumping Plt #3, CA, so most years bring a freeze but some pass without one.
What growing zone is Clayton in?
Zone 9b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 27°.
What is the best time of year to visit Clayton?
By one simple rule (highs of 62–84° and lows of 40° or more), March, April, May, June, October and November. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Clayton getting warmer?
Yes: 1991–2020 averaged 1.6° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 63% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Clayton.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.