Summer arrives in force in Unionville, hotter than in 91% of Canadian towns
January mornings start at about −10.1°C. Frost is rarer than in 70% of Canadian towns: about 145 nights a year drop below freezing. Of all months, June brings the most precipitation and February the least. Windshields need scraping on about 145 mornings a year, the days the air reaches 0°C or below.
These are not Unionville’s own readings: ECCC keeps no normals there, so the page uses Toronto Buttonville (Airport), 4.3 km west.
A year in Unionville at a glance
Each month’s typical high and low, in °C.
What stands out about Unionville’s climate
Compared with Canadian towns, with its place among towns of 2,500+ in Ontario beside it.
What a year in Unionville feels like
Typical highs and lows by season and by month, from ECCC’s 1991–2020 normals.
Frost on 145 days, 20°C on 126
From October to May frost is routine, and in January it comes on almost every night. Deep cold, under −20°C, comes on about 6 nights a year.
Frost days by month
Average days at 0°C or below
Days above 20°C by month
Average days
862 mm of precipitation in a typical year
About 113 days a year bring 1 mm or more.
Rain and snow by month
Millimetres
Rain alone by month
Millimetres
Snowfall: about 146 cm in a normal year
Expect snow from November to April, with about 40 cm in January, the snowiest month.
Snowfall by month
Centimetres
Snow on the ground by month
Centimetres at month’s end
Heating a home in Unionville
93% of a year’s heating need falls between October and April. Months averaging under 10°C: October to April.
Each day the mean sits under 18°C adds its shortfall; a year’s total is its heating degree days. That means homes here need less heating than 74% of Canadian towns.
Living with Unionville’s climate
What the normals mean for a garden, a day outside and the depth of winter.
The frost-free stretch runs from about 3 May to about 13 October, some 161 days in a normal year.
Plan time outside for Jun, Aug and Sep: highs of 17–27°C and nights no colder than 8°C.
Parks & trails →Plan for about 22 days a year with a wind chill below −20.
About 55 days a year turn sultry, with the humidex past 30.
Ice storms, floods and heat waves are risks, not averages: they are on Unionville’s hazards page.
Flood & hazards →ECCC’s normals location: Toronto Buttonville (Airport)
ECCC builds the Toronto Buttonville (Airport) normals from 3 stations’ records over 1991–2020, joined where one replaced another.
| Distance from the town | 4.3 km west |
| 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), 23 km |
How Unionville 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 Unionville’s own would show the same figures). The nearest places to Unionville with figures are 17–29 km away.
| Town | July high | January low | Rain & snow |
|---|---|---|---|
| Unionville Toronto Buttonville (Airport) | 27.3°C | −10.1°C | 862 mm |
| Pickering 17 km · Oshawa | 25.7°C 1.6°C cooler | −8.9°C 1.2°C milder | 906 mm |
| Toronto 18 km · Toronto (City) | 27.0°C about the same | −6.7°C 3.4°C milder | 823 mm |
| East Gwillimbury 29 km · Udora | 26.3°C 1.0°C cooler | −11.7°C 1.6°C colder | 883 mm |
Unionville weather by month
Month by month, 1991–2020: the usual high, low and mean, the rain and snow, and the snowfall.
| 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 |
January strays furthest from its normal year to year, by 3.1°C; June the least
Bars run from each month’s record low to its record high since 1991. March spans the most, from −25.6°C (2003) to 26.3°C (2012).
Where Unionville’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: a sunshine figure (ECCC published none for 1991–2020) and any lapse-rate correction for height, as the town has no elevation here.
Canadian Climate Normals 1991–2020 · ECCC Data Services End-use Licence. Data Source: Environment and Climate Change Canada
Questions about Unionville’s climate
How warm does Unionville get in summer?
Afternoons average 27.3°C in July, the warmest time of year.
How cold does Unionville get in winter?
Winter bottoms out in January, with lows near −10.1°C.
How much rain and snow does Unionville get?
Measured as water, a year brings 862 mm: 87 mm in June, the wettest month, and 51 mm in February, the driest.
How long does snow stay on the ground?
Count on about 76 days of snow cover a year, 1 cm or deeper.
Are these figures for Unionville itself?
The figures are ECCC’s for Toronto Buttonville (Airport); Unionville has no normals station.
Data Source: Environment and Climate Change Canada · ECCC Data Services End-use Licence Today’s forecast for Unionville →
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).