Northbrook climate — normals and trends
Northbrook (United States) has a hot-summer humid continental climate (Dfa) under the Köppen-Geiger classification. Its mean annual temperature is 9.2 °C and it receives 1,001 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 (23.3 °C on average) and the coldest is January (-4.5 °C). Rainfall peaks in April.
Northbrook averages 103 frost days, 6 hot days (≥ 30 °C) and 123 rainy days per year.
Northbrook has warmed by +1.2 °C between 1940 and 2025, or +0.14 °C per decade. This trend is statistically significant.
The number of frost days there went from about 121 to 85 per year over the period.
The hottest day of the period reached 35.3 °C (on 30 July 1999) and the coldest -30.3 °C (on 19 January 1994).
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
NorthbrookIllinois
- coords
- 42.13°, -87.83°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
9.2°C
Average daily high
11.6°C
Average daily low
7.1°C
Annual rainfall
1,001mm
Sunshine / day
9.0h
Mean relative humidity
76%
Average peak wind
28.8km/h
Seasonal range
27.8°C
Frost days (< 0 °C)
103 d/yr
Hot days (≥ 30 °C)
6 d/yr
Rainy days (≥ 1 mm)
123 d/yr
Annual snowfall
82.9 cm
Average feels-like high
9.0 °C
Average feels-like low
3.1 °C
Average peak gust
40.9 km/h
Tropical nights (≥ 20 °C)
59 d/yr
Solar radiation
14.9 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+1.2 °C
since 1940
+0.1 °C per decade · r² = 0.14 · 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
35.3 °C
30 July 1999
Coldest day
-30.3 °C
19 January 1994
Wettest day
92 mm
13 September 2008
Windiest day
71.4 km/h
22 February 1974
Strongest gust
105.1 km/h
11 November 1940
Hottest feels-like
43.4 °C
14 July 1995
Coldest feels-like
-39.1 °C
20 January 1985
Snowiest day
24.9 cm
1 December 2006
Sunniest day
14.7 h
11 June 2019
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 | -1.2 °C | +0.5 °C | 35 mm | -34 mm |
| Feb | 0.0 °C | +1.2 °C | 34 mm | -23 mm |
| Mar | 7.0 °C | +4.5 °C | 99 mm | +16 mm |
| Apr | 9.2 °C | +1.8 °C | 80 mm | -28 mm |
| May | 11.2 °C | -2.8 °C | 96 mm | +3 mm |
| Jun | 20.1 °C | -1.8 °C | 104 mm | +19 mm |
| Jul | 24.4 °C | -1.2 °C | 100 mm | +19 mm |
| Aug | 23.5 °C | -1.7 °C | 50 mm | -34 mm |
| Sep | 21.2 °C | -0.2 °C | 21 mm | -62 mm |
| Oct | 16.4 °C | +1.4 °C | 74 mm | -15 mm |
| Nov | 8.6 °C | +0.9 °C | 81 mm | -8 mm |
| Dec | 1.3 °C | -0.5 °C | 94 mm | +13 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 Northbrook?
Northbrook has a hot-summer humid continental climate (Köppen Dfa). Over 1940-2025, the average annual temperature is 9.2 °C and it receives 1,001 mm of precipitation per year.
What is the hottest day ever recorded in Northbrook?
The hottest day measured in Northbrook between 1940 and 2025 was 30 July 1999, reaching 35.3 °C.
What is the coldest day in Northbrook?
The coldest day measured in Northbrook between 1940 and 2025 was 19 January 1994, at -30.3 °C.
Does it snow in Northbrook?
Yes. Northbrook gets on average 82.9 cm of snow per year and has around 103 frost days.
Has the climate of Northbrook warmed?
Yes: Northbrook warmed by +1.2 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Northbrook?
The wettest day measured in Northbrook between 1940 and 2025 was 13 September 2008, with 92 mm of rain in 24 hours.
What was the windiest day in Northbrook?
The windiest day measured in Northbrook between 1940 and 2025 was 22 February 1974, with winds reaching 71.4 km/h.
What is the warmest month in Northbrook?
The warmest month in Northbrook is July (23.3 °C on average); the coldest is January (-4.5 °C).
How much does it rain in Northbrook?
Northbrook receives on average 1,001 mm of precipitation per year, spread over about 123 rainy days.
Is it sunny in Northbrook?
Northbrook gets on average 9.0 hours of sunshine per day, roughly 3,285 hours per year over 1940-2025.
What is the biggest single-day snowfall in Northbrook?
The heaviest 24-hour snowfall measured in Northbrook between 1940 and 2025 was 1 December 2006, with 24.9 cm.
Are there tropical nights in Northbrook?
Yes: Northbrook has on average 59 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Northbrook?
In Northbrook, between 1940 and 2025, the highest apparent temperature reached 43.4 °C on 14 July 1995, and the lowest was -39.1 °C on 20 January 1985.
Compare Northbrook with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Northbrook