July in Thornhill runs hotter than in 91% of Canadian towns
On a normal January night the air cools to about −10.1°C. The gap between a January night and a July afternoon is 37°C. Frost is rarer than in 70% of Canadian towns: about 145 nights a year drop below freezing. Picnics, hikes and garden evenings suit June, August and September, with highs of 22–26°C.
Borrowed figures: Thornhill has no normals station, so these come from Toronto Buttonville (Airport), 8.0 km north-east.
A year in Thornhill at a glance
Each month’s typical high and low, in °C.
What stands out about Thornhill’s climate
Compared with Canadian towns, with its place among towns of 2,500+ in Ontario beside it.
What a year in Thornhill feels like
Each season’s and each month’s usual high and low, 1991–2020.
145 frost days and 126 days above 20°C a year
Frost comes from October to May; in January almost every night freezes. Some 6 nights a year drop under −20°C.
Frost days by month
Average days at 0°C or below
Days above 20°C by month
Average days
About 862 mm of rain and snow a year
June brings the most rain and snow; February, the least. On about 113 days a year, 1 mm or more falls.
Rain and snow by month
Millimetres
Rain alone by month
Millimetres
Snowfall: about 146 cm in a normal year
Snow falls from November to April, most of all in January (about 40 cm).
Snowfall by month
Centimetres
Snow on the ground by month
Centimetres at month’s end
Heating a home in Thornhill
93% of a year’s heating need falls between October and April. Months averaging under 10°C: October to April.
The total grows by a degree for every degree a day’s mean sits under 18°C. A house here needs less heating than 74% of Canadian towns.
Living with Thornhill’s climate
Gardening, time outside, winter cold and summer heat, from the 1991–2020 normals.
Count on about 161 frost-free days: the last frost averages 3 May, the first 13 October.
The outdoor season by the averages is Jun, Aug and Sep, with highs of 17–27°C and lows of 8°C or more.
Parks & trails →Roughly 22 days a year feel colder than −20 in the wind.
Humid heat, a humidex over 30, comes on about 55 days a year.
Storms, floods and heat waves sit outside these normals; Thornhill’s hazards page covers them.
Flood & hazards →ECCC’s normals location: Toronto Buttonville (Airport)
Behind the 1991–2020 normals for Toronto Buttonville (Airport) are 3 stations, which ECCC combines into one record.
| Distance from the town | 8.0 km north-east |
| Station altitude | 198 m |
| Completeness | meets the WMO “3 and 5” rule |
| WMO standard normals | No |
| Coldest reading, 1991–2020 | −35.2°C |
| Hottest reading, 1991–2020 | 37.8°C |
| Average wind | 12.2 km/h on average, most often from the north |
| Next-nearest location | Toronto (City), 15 km |
How Thornhill compares
Compared with 2,611 towns and neighbourhoods of 2,500 or more across Canada; the dots mark the other normals locations in Ontario.
Nearby towns’ climate
Nearby places read from a different ECCC location (places on Thornhill’s own would show the same figures). Distances here run 11–30 km: that is how far the nearest places with figures are from Thornhill.
| Town | July high | January low | Rain & snow |
|---|---|---|---|
| Thornhill Toronto Buttonville (Airport) | 27.3°C | −10.1°C | 862 mm |
| Toronto 11 km · Toronto (City) | 27.0°C about the same | −6.7°C 3.4°C milder | 823 mm |
| Pickering 27 km · Oshawa | 25.7°C 1.6°C cooler | −8.9°C 1.2°C milder | 906 mm |
| Brampton 28 km · Toronto Pearson (Airport) | 27.4°C about the same | −8.9°C 1.2°C milder | 807 mm |
Thornhill weather by month
Average daily high and low, mean temperature, rain and snow (as water) and snowfall by month, 1991–2020.
| Month | High | Low | Mean | Rain & snow | Snow |
|---|---|---|---|---|---|
| January | −1.7°C | −10.1°C | −6.0°C | 64 mm | 40 cm |
| February | −1.0°C | −10.1°C | −5.6°C | 51 mm | 34 cm |
| March | 4.6°C | −5.0°C | −0.2°C | 52 mm | 20 cm |
| April | 11.8°C | 1.2°C | 6.5°C | 79 mm | 7 cm |
| May | 19.3°C | 7.4°C | 13.4°C | 80 mm | under 1 cm |
| June | 24.6°C | 13.0°C | 18.8°C | 87 mm | 0 cm |
| July | 27.3°C | 15.6°C | 21.5°C | 85 mm | 0 cm |
| August | 26.3°C | 14.8°C | 20.6°C | 72 mm | 0 cm |
| September | 21.9°C | 10.4°C | 16.2°C | 83 mm | 0 cm |
| October | 14.3°C | 4.3°C | 9.4°C | 71 mm | 1 cm |
| November | 7.4°C | −0.8°C | 3.3°C | 77 mm | 12 cm |
| December | 1.5°C | −5.8°C | −2.2°C | 63 mm | 33 cm |
| Year | 13.0°C | 2.9°C | 8.0°C | 862 mm | 146 cm |
A March here can run from −25.6°C to 26.3°C
January is the least predictable month: about two years in three its average lands within 3.1°C of the normal, −6.0°C. June is the steadiest, within 1.2°C.
Where Thornhill’s numbers come from
Averages over 30 years, not a forecast.
- Normals: the 1991–2020 Canadian Climate Normals at Toronto Buttonville (Airport), the closest ECCC location with twelve months of temperature normals.
- Comparisons: every place of 2,500+ in Canada but the city hubs and the reserves, each on its nearest ECCC location.
- 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 Thornhill’s climate
How warm does Thornhill get in summer?
The year’s warmest days come in July, with highs averaging 27.3°C.
How cold does Thornhill get in winter?
In January, the coldest month, the typical low is −10.1°C.
How much rain and snow does Thornhill get?
Count on roughly 862 mm a year, heaviest in June (87 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 76 days a year.
Are these figures for Thornhill itself?
Not exactly. Thornhill lacks a normals station, so Toronto Buttonville (Airport) supplies the figures.
Data Source: Environment and Climate Change Canada · ECCC Data Services End-use Licence Today’s forecast for Thornhill →
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).