Photo: P199 · Public domainNights turn raw in Chalk River each January, colder than in 83% of Canadian towns
July afternoons average 26.3°C. Of all months, June brings the most precipitation and February the least. Summer afternoons here are warmer than in 63% of Canadian towns. The outdoor season runs from June to August, with highs of 24–26°C.
Chalk River has no ECCC normals station of its own: every figure here comes from Petawawa, 16 km south-east.
A year in Chalk River at a glance
Each month’s typical high and low, in °C.
What stands out about Chalk River’s climate
Compared with Canadian towns, with its place among towns of 2,500+ in Ontario beside it.
What a year in Chalk River feels like
Typical highs and lows by season and by month, from ECCC’s 1991–2020 normals.
About 932 mm of rain and snow a year
On about 132 days a year, 1 mm or more falls.
Rain and snow by month
Millimetres
Rain alone by month
Millimetres
199 cm of snow in a typical year
From October to April snow is likely; January is the peak, at about 49 cm.
Snowfall by month
Centimetres
Snow on the ground by month
Centimetres at month’s end
Living with Chalk River’s climate
Gardening, time outside, winter cold and summer heat, from the 1991–2020 normals.
Warm afternoons without cold nights, 17–27°C and 8°C or more, mark Jun, Jul and Aug.
Parks & trails →The wind chill passes −20 on about 52 days in a normal year.
Roughly 46 days a year feel hotter than 30 once humidity is counted.
Storms, floods and heat waves sit outside these normals; Chalk River’s hazards page covers them.
Flood & hazards →ECCC’s normals location: Petawawa
Behind the 1991–2020 normals for Petawawa are 3 stations, which ECCC combines into one record.
| Distance from the town | 16 km south-east |
| Station altitude | 130 m |
| Completeness | at least 20 years |
| WMO standard normals | No |
| Coldest reading, 1991–2020 | −39.8°C |
| Hottest reading, 1991–2020 | 36.9°C |
| Average wind | 9.6 km/h on average, most often from the south-east |
| Next-nearest location | Charteris, 91 km |
How Chalk River compares
Against the 2,611 Canadian towns and neighbourhoods of 2,500 or more, each read from its own normals location; the dots are the other locations those towns use in Ontario.
Nearby towns’ climate
Nearby places read from a different ECCC location (places on Chalk River’s own would show the same figures). The nearest places to Chalk River with figures are 59–75 km away.
| Town | July high | January low | Rain & snow |
|---|---|---|---|
| Chalk River Petawawa | 26.3°C | −17.9°C | 932 mm |
| Whitewater Region 59 km · Charteris | 26.4°C about the same | −16.9°C 1.0°C milder | 932 mm |
| Barry's Bay 63 km · Bancroft | 25.7°C 0.6°C cooler | −17.1°C 0.8°C milder | 932 mm |
Chalk River weather by month
Each month’s normals, 1991–2020: high, low, mean, precipitation and snowfall.
| Month | High | Low | Mean | Rain & snow | Snow |
|---|---|---|---|---|---|
| January | −6.1°C | −17.9°C | −11.9°C | 68 mm | 49 cm |
| February | −3.6°C | −16.6°C | −10.2°C | 51 mm | 38 cm |
| March | 2.7°C | −10.0°C | −3.7°C | 58 mm | 27 cm |
| April | 10.8°C | −2.0°C | 4.5°C | 79 mm | 11 cm |
| May | 19.2°C | 4.5°C | 12.0°C | 85 mm | 1 cm |
| June | 24.0°C | 10.0°C | 17.0°C | 96 mm | 0 cm |
| July | 26.3°C | 12.3°C | 19.3°C | 89 mm | 0 cm |
| August | 25.2°C | 11.6°C | 18.4°C | 90 mm | 0 cm |
| September | 20.6°C | 7.3°C | 14.0°C | 83 mm | 0 cm |
| October | 12.8°C | 2.1°C | 7.5°C | 83 mm | 3 cm |
| November | 4.8°C | −4.1°C | 0.3°C | 77 mm | 25 cm |
| December | −2.4°C | −11.9°C | −7.3°C | 72 mm | 45 cm |
| Year | 11.2°C | −1.2°C | 5.0°C | 932 mm | 199 cm |
The most changeable month: December, give or take 3.1°C; the steadiest, June
Each bar spans a month’s coldest and warmest readings over thirty years; March’s run from −33.4°C in 2007 to 28.8°C in 2012.
Where Chalk River’s numbers come from
Averages over 30 years, not a forecast.
- Normals: the 1991–2020 Canadian Climate Normals at Petawawa, the closest ECCC location with twelve months of temperature normals.
- Comparisons: the towns and neighbourhoods of 2,500+ across Canada, each on its nearest normals location, without the city totals or the reserves.
- Not on this page: sunshine, not in ECCC’s 1991–2020 normals, and the effect of the town’s height, for which there is no figure.
Canadian Climate Normals 1991–2020 · ECCC Data Services End-use Licence. Data Source: Environment and Climate Change Canada
Questions about Chalk River’s climate
How warm does Chalk River get in summer?
Highs reach 26.3°C on an average July day; no month is warmer.
How cold does Chalk River get in winter?
Of all twelve months, January has the coldest nights, about −17.9°C.
How much rain and snow does Chalk River get?
Count on roughly 932 mm a year, heaviest in June (96 mm) and lightest in February (51 mm).
How long does snow stay on the ground?
There is 1 cm of snow or more on the ground on roughly 140 days a year.
Are these figures for Chalk River itself?
Only indirectly: the readings are made at Petawawa, outside Chalk River.
Data Source: Environment and Climate Change Canada · ECCC Data Services End-use Licence Today’s forecast for Chalk River →
Adapted from Statistics Canada (Census of Population 2021, population estimates 2025, 2021 census boundaries) under the Statistics Canada Open Licence; this does not constitute an endorsement by Statistics Canada. Neighbourhood names in some cities © OpenStreetMap contributors (ODbL).