Photo: NHRHS2010 · CC BY-SA 3.0Precipitation in Los Alamos trails that of 92% of U.S. towns: 17 inches a year
The depth of winter brings overnight lows near 40°. Expect the heaviest rain or snow in February and the lightest in August. By January nights alone, it runs milder than 88% of U.S. towns. The outdoor season runs from February to July and September to November, with highs of 65–84°.
A year in Los Alamos at a glance
Each month’s typical high and low, and what it brings.
What stands out about Los Alamos’ climate
Compared with towns across the U.S., with Los Alamos’ place in California beside it.
What a year in Los Alamos feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 315 frost-free days a year
In half of years the last 32° night comes by February 4 and the first by December 13. Frost and day counts come from Santa Maria Public Airport, 15 miles away.
The 2023 USDA map puts Los Alamos’ center in zone 9a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 25°. 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 17 inches of rain a year
February is the wettest month and August the driest. Rain falls on about 41 days a year. Snow is rare: about 0.0" in a normal year at Los Alamos, CA, so most winters see none.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Los Alamos
94% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from December through February.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Santa Maria Public Airport.
Living with Los Alamos’ climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
315 frost-free days in zone 9a. The last frost comes by Feb 4 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Dec 13.
Months with highs of 62–84° and lows of 40° or more: February, March, April, May, June, July, September, October and November. 0.0 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Los Alamos from natural hazards, drought is the largest share (33%). Normals are averages; the hazards page covers the extremes.
Natural hazards →Los Alamos and similar climates
TownRatings has no climate map of the towns around Los Alamos yet.
Climates most like Los Alamos’, 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 |
|---|---|---|---|---|
| Los Alamos, CA | 40° | 84° | 17" | 0.0" |
| Green, OR | 37° | 86° | 32" | 0.0" |
| Sierra Vista Southeast, AZ | 32° | 91° | 15" | 0.7" |
| Alpine, TX | 30° | 90° | 15" | 2.2" |
| Kennewick, WA | 29° | 90° | 8" | 2.0" |
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
Warmer than it used to be
The last 30 years in Los Alamos averaged 2.3° warmer than the 1900s. The biggest change is in January (+3.0°).
A bigger shift than in 97% 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 Los Alamos compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Los Alamos’ place among California’s.
Los Alamos weather by month
Highs, lows and precipitation from NOAA’s grid at Los Alamos’ center; snow, wet days and snow on the ground from Los Alamos, CA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 65° | 40° | 3.7" | 0.0" | 8 | 0 | 49° – 58° |
| February | 65° | 41° | 3.9" | 0.0" | 9 | 0 | 48° – 58° |
| March | 68° | 43° | 3.0" | 0.0" | 6 | 0 | 49° – 61° |
| April | 71° | 45° | 1.1" | 0.0" | 3 | 0 | 54° – 62° |
| May | 75° | 49° | 0.3" | 0.0" | 2 | 0 | 58° – 67° |
| June | 79° | 52° | 0.0" | 0.0" | 1 | 0 | 62° – 69° |
| July | 84° | 56° | 0.0" | 0.0" | 0 | 0 | 67° – 73° |
| August | 84° | 56° | 0.0" | 0.0" | 0 | 0 | 67° – 73° |
| September | 83° | 54° | 0.1" | 0.0" | 0 | 0 | 65° – 74° |
| October | 78° | 49° | 0.7" | 0.0" | 2 | 0 | 60° – 70° |
| November | 71° | 43° | 1.4" | 0.0" | 4 | 0 | 50° – 61° |
| December | 64° | 39° | 2.5" | 0.0" | 6 | 0 | 48° – 55° |
| Year | 74° | 47° | 16.7" | 0.0" | 41 | 0 |
How much a month can swing
A normal is an average. March swings the most: from 1991 to 2020 its average ranged from 49° to 61°. August is the most reliable, staying within 6°.
Where Los Alamos’ 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 Los Alamos’ center.
- Snow: Los Alamos, CA (NOAA station in town).
- Frost, freezing nights, 90° and 100° days, heating and cooling: Santa Maria Public Airport, 15 miles from the town’s center, 340 ft lower; no station nearby passes every check; this is the nearest one in the same valley, flagged above.
- 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 Los Alamos’ climate
What is the weather like in Los Alamos?
A typical July afternoon reaches 84°, a January night drops to 40°, and snow is almost unheard of. Milder January nights than 88% of U.S. towns; cooler July afternoons than 62% of U.S. towns.
How cold does it get in Los Alamos in winter?
December nights average 39°. About 9 nights a year reach 32° or below. In the coldest December of the last 30 years the month averaged 48°.
How much snow does Los Alamos get?
About 0.0 inches in a normal winter at Los Alamos, CA, so most winters see none.
How hot does it get in Los Alamos?
July, with a typical high of 84° and a low of 56°. About 6 days a year reach 90° (Santa Maria Public Airport).
When is the first and last frost in Los Alamos?
In half of years the last spring frost (32°) comes by February 4 and the first fall frost by December 13, about 315 frost-free days, at Santa Maria Public Airport.
What growing zone is Los Alamos in?
Zone 9a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 25°.
What is the best time of year to visit Los Alamos?
By one simple rule (highs of 62–84° and lows of 40° or more), February, March, April, May, June, July, September, October and November. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Los Alamos getting warmer?
Yes: 1991–2020 averaged 2.3° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 97% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Los Alamos.
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.