Millbrae climate — normals and trends
Millbrae (United States) has a warm-summer mediterranean climate (Csb) under the Köppen-Geiger classification. Its mean annual temperature is 13.0 °C and it receives 508 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 September (15.7 °C on average) and the coldest is January (10.4 °C). Rainfall peaks in January.
Millbrae averages 0 frost days, 0 hot days (≥ 30 °C) and 57 rainy days per year.
Millbrae has warmed by +0.6 °C between 1940 and 2025, or +0.07 °C per decade. This trend is statistically significant.
The hottest day of the period reached 30.9 °C (on 1 September 2017) and the coldest -0.9 °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
MillbraeCalifornia
- coords
- 37.60°, -122.39°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
13.0°C
Average daily high
15.4°C
Average daily low
11.1°C
Annual rainfall
508mm
Sunshine / day
10.5h
Mean relative humidity
82%
Average peak wind
19.9km/h
Seasonal range
5.3°C
Frost days (< 0 °C)
0 d/yr
Hot days (≥ 30 °C)
0 d/yr
Rainy days (≥ 1 mm)
57 d/yr
Annual snowfall
0.0 cm
Average feels-like high
14.3 °C
Average feels-like low
9.0 °C
Average peak gust
34.6 km/h
Tropical nights (≥ 20 °C)
0 d/yr
Solar radiation
18.2 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+0.6 °C
since 1940
+0.1 °C per decade · r² = 0.09 · p = 0.005
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
30.9 °C
1 September 2017
Coldest day
-0.9 °C
22 December 1990
Wettest day
86 mm
25 January 2008
Windiest day
60.0 km/h
3 December 1983
Strongest gust
113.4 km/h
6 February 1998
Hottest feels-like
33.0 °C
1 September 2017
Coldest feels-like
-6.8 °C
22 January 1962
Snowiest day
0.7 cm
13 March 1975
Sunniest day
14.2 h
3 July 2024
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 | 13.5 °C | +1.0 °C | 13 mm | -82 mm |
| Feb | 13.6 °C | +0.4 °C | 112 mm | +20 mm |
| Mar | 13.5 °C | -0.1 °C | 81 mm | +2 mm |
| Apr | 13.8 °C | -0.3 °C | 14 mm | -25 mm |
| May | 15.0 °C | -0.1 °C | 3 mm | -13 mm |
| Jun | 15.2 °C | -1.3 °C | 0 mm | -4 mm |
| Jul | 15.7 °C | -1.8 °C | 1 mm | +1 mm |
| Aug | 18.0 °C | 0.0 °C | 5 mm | +3 mm |
| Sep | 19.3 °C | +0.7 °C | 3 mm | -1 mm |
| Oct | 18.0 °C | +0.4 °C | 31 mm | +6 mm |
| Nov | 15.7 °C | +0.7 °C | 79 mm | +18 mm |
| Dec | 13.5 °C | +0.6 °C | 65 mm | -25 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 Millbrae?
Millbrae has a warm-summer mediterranean climate (Köppen Csb). Over 1940-2025, the average annual temperature is 13.0 °C and it receives 508 mm of precipitation per year.
What is the hottest day ever recorded in Millbrae?
The hottest day measured in Millbrae between 1940 and 2025 was 1 September 2017, reaching 30.9 °C.
What is the coldest day in Millbrae?
The coldest day measured in Millbrae between 1940 and 2025 was 22 December 1990, at -0.9 °C.
Does it snow in Millbrae?
Almost never: Millbrae sees virtually no snow, with about 0 frost days per year.
Has the climate of Millbrae warmed?
Yes: Millbrae warmed by +0.6 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Millbrae?
The wettest day measured in Millbrae between 1940 and 2025 was 25 January 2008, with 86 mm of rain in 24 hours.
What was the windiest day in Millbrae?
The windiest day measured in Millbrae between 1940 and 2025 was 3 December 1983, with winds reaching 60.0 km/h.
What is the warmest month in Millbrae?
The warmest month in Millbrae is September (15.7 °C on average); the coldest is January (10.4 °C).
How much does it rain in Millbrae?
Millbrae receives on average 508 mm of precipitation per year, spread over about 57 rainy days.
Is it sunny in Millbrae?
Millbrae gets on average 10.5 hours of sunshine per day, roughly 3,833 hours per year over 1940-2025.
What is the biggest single-day snowfall in Millbrae?
The heaviest 24-hour snowfall measured in Millbrae between 1940 and 2025 was 13 March 1975, with 0.7 cm.
Are there tropical nights in Millbrae?
Almost never: tropical nights (temperature staying above 20 °C) are virtually non-existent in Millbrae.
What was the most extreme apparent temperature in Millbrae?
In Millbrae, between 1940 and 2025, the highest apparent temperature reached 33.0 °C on 1 September 2017, and the lowest was -6.8 °C on 22 January 1962.
Compare Millbrae with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Millbrae