Los Altos climate — normals and trends
Los Altos (United States) has a warm-summer mediterranean climate (Csb) under the Köppen-Geiger classification. Its mean annual temperature is 14.4 °C and it receives 464 mm of precipitation per year.
These figures are normals computed over 86 complete calendar years, from 1940 to 2025, using ERA5 reanalysis data from the Copernicus programme.
The warmest month is July (19.9 °C on average) and the coldest is January (8.7 °C). Rainfall peaks in January.
Los Altos averages 2 frost days, 31 hot days (≥ 30 °C) and 54 rainy days per year.
Los Altos has warmed by +1.3 °C between 1940 and 2025, or +0.15 °C per decade. This trend is statistically significant.
The number of frost days there went from about 4 to 0 per year over the period.
The hottest day of the period reached 43.0 °C (on 3 September 1950) and the coldest -5.6 °C (on 22 December 1990).
Data from ERA5 reanalysis (Copernicus Climate Change Service), redistributed under a CC-BY 4.0 licence. Normals are recomputed whenever the archive is updated.
Climate normals · ERA5
Los AltosCalifornia
- coords
- 37.39°, -122.11°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
14.4°C
Average daily high
20.2°C
Average daily low
10.0°C
Annual rainfall
464mm
Sunshine / day
10.7h
Mean relative humidity
73%
Average peak wind
12.3km/h
Seasonal range
11.2°C
Frost days (< 0 °C)
2 d/yr
Hot days (≥ 30 °C)
31 d/yr
Rainy days (≥ 1 mm)
54 d/yr
Annual snowfall
0.2 cm
Average feels-like high
19.4 °C
Average feels-like low
8.7 °C
Average peak gust
29.6 km/h
Tropical nights (≥ 20 °C)
2 d/yr
Solar radiation
18.8 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+1.3 °C
since 1940
+0.2 °C per decade · r² = 0.35 · p = < 0.001
Trend fitted by linear regression (ordinary least squares) on annual means. A trend is shown only when it is statistically significant (p < 0.05).
A climograph overlays rainfall (bars) and temperature (line): the standard reading in climatology, where you can see at a glance whether the warm season is also the dry one.
Records for the period
Hottest day
43.0 °C
3 September 1950
Coldest day
-5.6 °C
22 December 1990
Wettest day
85 mm
13 October 2009
Windiest day
40.8 km/h
19 December 1955
Strongest gust
105.8 km/h
14 February 1986
Hottest feels-like
43.0 °C
2 July 1991
Coldest feels-like
-9.6 °C
22 December 1990
Snowiest day
3.1 cm
5 December 1952
Sunniest day
14.1 h
9 July 2025
Normals computed over complete calendar years 1940–2025.
A specific year
Pick a year and see how it compares to normal — warmer, drier or more extreme than usual?
Across the whole year
Month by month
| High | vs. normal | Precipitation | vs. normal | |
|---|---|---|---|---|
| Jan | 15.3 °C | +2.1 °C | 9 mm | -76 mm |
| Feb | 15.8 °C | +1.0 °C | 110 mm | +27 mm |
| Mar | 16.1 °C | 0.0 °C | 85 mm | +10 mm |
| Apr | 18.6 °C | +0.3 °C | 21 mm | -20 mm |
| May | 22.1 °C | +1.0 °C | 3 mm | -14 mm |
| Jun | 23.4 °C | -1.2 °C | 0 mm | -4 mm |
| Jul | 24.6 °C | -2.8 °C | 0 mm | -1 mm |
| Aug | 26.8 °C | -0.3 °C | 3 mm | +1 mm |
| Sep | 25.9 °C | -0.5 °C | 4 mm | +0 mm |
| Oct | 21.5 °C | -1.2 °C | 32 mm | +10 mm |
| Nov | 17.6 °C | +0.5 °C | 76 mm | +23 mm |
| Dec | 14.0 °C | +0.5 °C | 46 mm | -32 mm |
The year's extremes
What was the weather like that day?
Your birthday, a wedding, a memorable trip: discover the actual weather for any date since 1940.
Frequently asked questions
What is the climate of Los Altos?
Los Altos has a warm-summer mediterranean climate (Köppen Csb). Over 1940-2025, the average annual temperature is 14.4 °C and it receives 464 mm of precipitation per year.
What is the hottest day ever recorded in Los Altos?
The hottest day measured in Los Altos between 1940 and 2025 was 3 September 1950, reaching 43.0 °C.
What is the coldest day in Los Altos?
The coldest day measured in Los Altos between 1940 and 2025 was 22 December 1990, at -5.6 °C.
Does it snow in Los Altos?
Almost never: Los Altos sees virtually no snow, with about 2 frost days per year.
Has the climate of Los Altos warmed?
Yes: Los Altos warmed by +1.3 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Los Altos?
The wettest day measured in Los Altos between 1940 and 2025 was 13 October 2009, with 85 mm of rain in 24 hours.
What was the windiest day in Los Altos?
The windiest day measured in Los Altos between 1940 and 2025 was 19 December 1955, with winds reaching 40.8 km/h.
What is the warmest month in Los Altos?
The warmest month in Los Altos is July (19.9 °C on average); the coldest is January (8.7 °C).
How much does it rain in Los Altos?
Los Altos receives on average 464 mm of precipitation per year, spread over about 54 rainy days.
Is it sunny in Los Altos?
Los Altos gets on average 10.7 hours of sunshine per day, roughly 3,905 hours per year over 1940-2025.
What is the biggest single-day snowfall in Los Altos?
The heaviest 24-hour snowfall measured in Los Altos between 1940 and 2025 was 5 December 1952, with 3.1 cm.
Are there tropical nights in Los Altos?
Yes: Los Altos has on average 2 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Los Altos?
In Los Altos, between 1940 and 2025, the highest apparent temperature reached 43.0 °C on 2 July 1991, and the lowest was -9.6 °C on 22 December 1990.
Compare Los Altos with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Los Altos