Photo: Ken Lund from Reno, Nevada, USA · CC BY-SA 2.0Frosty mornings in St. Thomas are scarcer than in 75% of Canadian towns
In July the day’s top temperature is typically 26.6°C. Summer afternoons here are warmer than in 70% of Canadian towns. The year swings widely: the coldest month’s nights and the warmest month’s afternoons are 36°C apart. The outdoor season runs from June to September, with highs of 22–27°C.
The nearest ECCC normals location to St. Thomas is London, 28 km north, and every figure on this page is its.
A year in St. Thomas at a glance
Each month’s typical high and low, in °C.
What stands out about St. Thomas’s climate
Compared with Canadian towns, with its place among towns of 2,500+ in Ontario beside it.
What a year in St. Thomas feels like
Each season’s and each month’s usual high and low, 1991–2020.
139 frost days and 128 days above 20°C a year
The frost season runs October to May, and January freezes nearly every night. Heat of 30°C or more comes on about 11 days a year.
Frost days by month
Average days at 0°C or below
Days above 20°C by month
Average days
About 962 mm of rain and snow a year
September is the wettest month and February the driest. On about 128 days a year, 1 mm or more falls.
Rain and snow by month
Millimetres
152 cm of snow in a typical year
The snow season runs October to April; January brings the most, about 43 cm.
Snowfall by month
Centimetres
Snow on the ground by month
Centimetres at month’s end
London publishes no full year of snowfall, so these figures come from Strathroy-Mullifarry, 44 km away.
Heating a home in St. Thomas
92% of a year’s heating need falls between October and April. Months averaging under 10°C: October to April.
Measured against 18°C: each day’s shortfall in mean temperature, added over twelve months. That means homes here need less heating than 79% of Canadian towns.
Living with St. Thomas’s climate
What the normals mean for a garden, a day outside and the depth of winter.
Seedlings can go out once the average last frost, around 3 May, has passed; autumn’s first, near 16 October, ends a season of about 165 days.
Warm afternoons without cold nights, 17–27°C and 8°C or more, mark Jun, Jul, Aug and Sep.
Parks & trails →Winter brings about 18 days with a wind chill below −20.
About 55 days a year turn sultry, with the humidex past 30.
For blizzards, floods and wildfire, turn to St. Thomas’s hazards page.
Flood & hazards →ECCC’s normals location: London
ECCC builds the London normals from 3 stations’ records over 1991–2020, joined where one replaced another.
| Distance from the town | 28 km north |
| Station altitude | 278 m |
| Completeness | meets the WMO “3 and 5” rule |
| WMO standard normals | No |
| Snowfall from | Strathroy-Mullifarry, 44 km |
| Coldest reading, 1991–2020 | −29.1°C |
| Hottest reading, 1991–2020 | 37.0°C |
| Average wind | 14.0 km/h on average, most often from the west |
| Next-nearest location | Strathroy-Mullifarry, 44 km |
How St. Thomas compares
Placed among 2,611 Canadian towns and neighbourhoods of 2,500+, each on its nearest normals location; each dot is another location used in Ontario.
Nearby towns’ climate
Nearby places read from a different ECCC location (places on St. Thomas’s own would show the same figures). Distances here run 20–30 km: that is how far the nearest places with figures are from St. Thomas.
St. Thomas 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 | −1.6°C | −9.1°C | −5.4°C | 79 mm | 43 cm |
| February | −0.6°C | −9.0°C | −4.8°C | 63 mm | 32 cm |
| March | 4.6°C | −4.5°C | 0.1°C | 67 mm | 20 cm |
| April | 12.2°C | 1.4°C | 6.8°C | 89 mm | 5 cm |
| May | 19.3°C | 7.7°C | 13.5°C | 89 mm | under 1 cm |
| June | 24.4°C | 13.2°C | 18.8°C | 86 mm | 0 cm |
| July | 26.6°C | 15.3°C | 21.0°C | 81 mm | 0 cm |
| August | 25.7°C | 14.4°C | 20.1°C | 67 mm | 0 cm |
| September | 22.1°C | 10.5°C | 16.3°C | 93 mm | 0 cm |
| October | 14.7°C | 5.0°C | 9.9°C | 83 mm | 2 cm |
| November | 7.5°C | −0.3°C | 3.6°C | 88 mm | 13 cm |
| December | 1.4°C | −5.2°C | −2.0°C | 79 mm | 37 cm |
| Year | 13.0°C | 3.3°C | 8.2°C | 962 mm | 152 cm |
February varies most from one year to the next (3.0°C), June least
March has the widest record range, −25.6°C in 2003 to 27.2°C in 2012; the tick on each bar is the month’s normal.
Where St. Thomas’s numbers come from
Averages over 30 years, not a forecast.
- Normals: the Canadian Climate Normals, 1991–2020, at London (the closest location with all twelve months of temperatures).
- Other locations: ECCC blanks a month that fails its completeness rule, so the precipitation or snowfall here comes from the next location with all twelve months.
- Comparisons: all Canadian places of 2,500 or more except city totals and reserves, each read the same way.
- Not on this page: sunshine, absent from every 1991–2020 location, and an altitude correction, for want of the town’s own elevation.
Canadian Climate Normals 1991–2020 · ECCC Data Services End-use Licence. Data Source: Environment and Climate Change Canada
Questions about St. Thomas’s climate
How warm does St. Thomas get in summer?
Midsummer means July, with afternoons near 26.6°C on a typical day.
How cold does St. Thomas get in winter?
On a normal January night the air drops to −9.1°C, the coldest of the year.
How much rain and snow does St. Thomas get?
Rain and snow add up to about 962 mm of water a year; September brings the most (93 mm), February the least (63 mm).
Are these figures for St. Thomas itself?
No, they come from London; ECCC keeps no 1991–2020 normals in St. Thomas itself.
Data Source: Environment and Climate Change Canada · ECCC Data Services End-use Licence Today’s forecast for St. Thomas →
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).