Ottawa climate — normals and trends
Ottawa (United States) has a hot-summer humid continental climate (Dfa) under the Köppen-Geiger classification. Its mean annual temperature is 10.3 °C and it receives 945 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 (23.5 °C on average) and the coldest is January (-4.9 °C). Rainfall peaks in May.
Ottawa averages 117 frost days, 30 hot days (≥ 30 °C) and 116 rainy days per year.
Ottawa has warmed by +2.1 °C between 1940 and 2025, or +0.25 °C per decade. This trend is statistically significant.
The number of frost days there went from about 130 to 104 per year over the period.
The hottest day of the period reached 39.6 °C (on 7 July 2012) and the coldest -33.2 °C (on 31 January 2019).
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
OttawaIllinois
- coords
- 41.35°, -88.84°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
10.3°C
Average daily high
15.2°C
Average daily low
5.5°C
Annual rainfall
945mm
Sunshine / day
8.8h
Mean relative humidity
70%
Average peak wind
20.4km/h
Seasonal range
28.4°C
Frost days (< 0 °C)
117 d/yr
Hot days (≥ 30 °C)
30 d/yr
Rainy days (≥ 1 mm)
116 d/yr
Annual snowfall
62.6 cm
Average feels-like high
13.2 °C
Average feels-like low
2.6 °C
Average peak gust
38.8 km/h
Tropical nights (≥ 20 °C)
30 d/yr
Solar radiation
15.0 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+2.1 °C
since 1940
+0.3 °C per decade · r² = 0.39 · 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
39.6 °C
7 July 2012
Coldest day
-33.2 °C
31 January 2019
Wettest day
97 mm
25 June 2021
Windiest day
55.1 km/h
3 April 1982
Strongest gust
111.6 km/h
10 November 1998
Hottest feels-like
44.2 °C
14 July 1995
Coldest feels-like
-38.9 °C
30 January 2019
Snowiest day
21.1 cm
13 March 1991
Sunniest day
14.3 h
9 June 2023
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 | -0.8 °C | +0.1 °C | 28 mm | -24 mm |
| Feb | 2.2 °C | +0.6 °C | 19 mm | -29 mm |
| Mar | 13.6 °C | +5.2 °C | 92 mm | +13 mm |
| Apr | 17.2 °C | +1.4 °C | 82 mm | -21 mm |
| May | 22.0 °C | +0.3 °C | 85 mm | -24 mm |
| Jun | 29.4 °C | +2.7 °C | 99 mm | -5 mm |
| Jul | 30.2 °C | +1.8 °C | 144 mm | +57 mm |
| Aug | 27.2 °C | -0.4 °C | 108 mm | +25 mm |
| Sep | 27.4 °C | +3.1 °C | 35 mm | -44 mm |
| Oct | 20.4 °C | +2.6 °C | 60 mm | -15 mm |
| Nov | 10.5 °C | +1.3 °C | 52 mm | -16 mm |
| Dec | 1.6 °C | -0.4 °C | 58 mm | -0 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 Ottawa?
Ottawa has a hot-summer humid continental climate (Köppen Dfa). Over 1940-2025, the average annual temperature is 10.3 °C and it receives 945 mm of precipitation per year.
What is the hottest day ever recorded in Ottawa?
The hottest day measured in Ottawa between 1940 and 2025 was 7 July 2012, reaching 39.6 °C.
What is the coldest day in Ottawa?
The coldest day measured in Ottawa between 1940 and 2025 was 31 January 2019, at -33.2 °C.
Does it snow in Ottawa?
Yes. Ottawa gets on average 62.6 cm of snow per year and has around 117 frost days.
Has the climate of Ottawa warmed?
Yes: Ottawa warmed by +2.1 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Ottawa?
The wettest day measured in Ottawa between 1940 and 2025 was 25 June 2021, with 97 mm of rain in 24 hours.
What was the windiest day in Ottawa?
The windiest day measured in Ottawa between 1940 and 2025 was 3 April 1982, with winds reaching 55.1 km/h.
What is the warmest month in Ottawa?
The warmest month in Ottawa is July (23.5 °C on average); the coldest is January (-4.9 °C).
How much does it rain in Ottawa?
Ottawa receives on average 945 mm of precipitation per year, spread over about 116 rainy days.
Is it sunny in Ottawa?
Ottawa gets on average 8.8 hours of sunshine per day, roughly 3,212 hours per year over 1940-2025.
What is the biggest single-day snowfall in Ottawa?
The heaviest 24-hour snowfall measured in Ottawa between 1940 and 2025 was 13 March 1991, with 21.1 cm.
Are there tropical nights in Ottawa?
Yes: Ottawa has on average 30 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Ottawa?
In Ottawa, between 1940 and 2025, the highest apparent temperature reached 44.2 °C on 14 July 1995, and the lowest was -38.9 °C on 30 January 2019.
Compare Ottawa with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Ottawa