Walnut climate — normals and trends
Walnut (United States) has a hot-summer mediterranean climate (Csa) under the Köppen-Geiger classification. Its mean annual temperature is 16.4 °C and it receives 425 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 August (23.2 °C on average) and the coldest is January (10.5 °C). Rainfall peaks in February.
Walnut averages 2 frost days, 57 hot days (≥ 30 °C) and 39 rainy days per year.
Walnut has warmed by +1.9 °C between 1940 and 2025, or +0.22 °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 43.6 °C (on 5 September 2020) and the coldest -5.1 °C (on 12 January 1949).
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
WalnutCalifornia
- coords
- 34.02°, -117.87°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
16.4°C
Average daily high
22.7°C
Average daily low
11.5°C
Annual rainfall
425mm
Sunshine / day
11.2h
Mean relative humidity
62%
Average peak wind
11.5km/h
Seasonal range
12.7°C
Frost days (< 0 °C)
2 d/yr
Hot days (≥ 30 °C)
57 d/yr
Rainy days (≥ 1 mm)
39 d/yr
Annual snowfall
1.4 cm
Average feels-like high
22.3 °C
Average feels-like low
10.4 °C
Average peak gust
31.8 km/h
Tropical nights (≥ 20 °C)
13 d/yr
Solar radiation
20.2 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+1.9 °C
since 1940
+0.2 °C per decade · r² = 0.48 · 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
43.6 °C
5 September 2020
Coldest day
-5.1 °C
12 January 1949
Wettest day
113 mm
1 March 1983
Windiest day
32.6 km/h
16 March 1964
Strongest gust
88.9 km/h
1 March 1983
Hottest feels-like
43.9 °C
6 September 2020
Coldest feels-like
-9.4 °C
12 January 1949
Snowiest day
7.7 cm
29 January 1957
Sunniest day
14.0 h
8 June 1940
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 | 18.0 °C | +1.6 °C | 19 mm | -68 mm |
| Feb | 19.2 °C | +2.2 °C | 102 mm | +10 mm |
| Mar | 17.6 °C | -0.5 °C | 73 mm | +2 mm |
| Apr | 20.3 °C | -0.2 °C | 17 mm | -14 mm |
| May | 23.8 °C | +1.0 °C | 7 mm | -3 mm |
| Jun | 26.7 °C | +0.4 °C | 5 mm | +3 mm |
| Jul | 28.1 °C | -1.8 °C | 0 mm | -1 mm |
| Aug | 30.8 °C | +0.5 °C | 1 mm | -3 mm |
| Sep | 28.6 °C | -0.3 °C | 18 mm | +11 mm |
| Oct | 25.0 °C | 0.0 °C | 44 mm | +28 mm |
| Nov | 21.1 °C | +0.6 °C | 125 mm | +85 mm |
| Dec | 20.2 °C | +3.3 °C | 100 mm | +36 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 Walnut?
Walnut has a hot-summer mediterranean climate (Köppen Csa). Over 1940-2025, the average annual temperature is 16.4 °C and it receives 425 mm of precipitation per year.
What is the hottest day ever recorded in Walnut?
The hottest day measured in Walnut between 1940 and 2025 was 5 September 2020, reaching 43.6 °C.
What is the coldest day in Walnut?
The coldest day measured in Walnut between 1940 and 2025 was 12 January 1949, at -5.1 °C.
Does it snow in Walnut?
Yes. Walnut gets on average 1.4 cm of snow per year and has around 2 frost days.
Has the climate of Walnut warmed?
Yes: Walnut warmed by +1.9 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Walnut?
The wettest day measured in Walnut between 1940 and 2025 was 1 March 1983, with 113 mm of rain in 24 hours.
What was the windiest day in Walnut?
The windiest day measured in Walnut between 1940 and 2025 was 16 March 1964, with winds reaching 32.6 km/h.
What is the warmest month in Walnut?
The warmest month in Walnut is August (23.2 °C on average); the coldest is January (10.5 °C).
How much does it rain in Walnut?
Walnut receives on average 425 mm of precipitation per year, spread over about 39 rainy days.
Is it sunny in Walnut?
Walnut gets on average 11.2 hours of sunshine per day, roughly 4,088 hours per year over 1940-2025.
What is the biggest single-day snowfall in Walnut?
The heaviest 24-hour snowfall measured in Walnut between 1940 and 2025 was 29 January 1957, with 7.7 cm.
Are there tropical nights in Walnut?
Yes: Walnut has on average 13 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Walnut?
In Walnut, between 1940 and 2025, the highest apparent temperature reached 43.9 °C on 6 September 2020, and the lowest was -9.4 °C on 12 January 1949.
Compare Walnut with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Walnut