Annual mean 10°C · wettest around April · prevailing wind W
Warmest
25.5 °C
Coldest
-2.4 °C
Wettest
24%
Windiest
4.1 m/s
Prevailing
W
3.4 m/s average
When this place is good five ratings · thirty-six ten-day sections · click a cell to read it
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Every reading
bars actual · line feels-like, °Cchance of rain, %wind speed, m/ssky covered, %
The average temperature in Sarnia over the whole year is 10°C. July is the hottest month, with highs of about 25°C; January is the coldest, with lows of about -4°C. Sarnia has no sharply defined rainy season: the chance of rain on a given day runs from 14% in August, the driest month, to 21% in April, the wettest. Winds in Sarnia are highest in March, averaging 3.4 m/s (12 km/h), and lightest in July, at 2.2 m/s (8 km/h). The prevailing wind is from the W. The clearest skies in Sarnia come in July, when the sky is typically 35% covered; January is the cloudiest month, at 73%.
Month by month Sarnia climate by month: average temperatures year round · click a month to read it
Month
High
Low
Feels like
Chance of rain
Cloud
Wind
Being outside
Sun
Walking
January
-2°C
-4°C
-8°C
16%
73%
3.1 m/s
0
0
1
February
0°C
-3°C
-6°C
14%
64%
3.2 m/s
0
0
5
March
4°C
0°C
-2°C
17%
57%
3.4 m/s
1
0
11
April
10°C
5°C
4°C
21%
55%
3.2 m/s
11
0
33
May
16°C
11°C
12°C
17%
46%
2.9 m/s
34
8
56
June
22°C
16°C
20°C
15%
37%
2.5 m/s
63
23
59
July
25°C
19°C
25°C
14%
35%
2.2 m/s
67
47
35
August
25°C
18°C
24°C
14%
38%
2.3 m/s
70
42
41
September
21°C
15°C
20°C
15%
44%
2.3 m/s
68
21
62
October
15°C
9°C
11°C
19%
54%
2.7 m/s
31
3
59
November
6°C
3°C
1°C
17%
59%
2.9 m/s
5
0
20
December
1°C
-1°C
-4°C
16%
72%
2.9 m/s
0
0
3
High and low are the warmest and coolest of four readings a day — midnight, 6am, noon and 6pm — so a true overnight low can sit a degree or two under them. Chance of rain, cloud and wind are the day’s average; feels-like and the three ratings (each out of 100: Good from 55, Ideal from 80) are read at midday.
Seasons, and the year in short Sarnia weather by season
Year round, Sarnia has days of about -2°C at their warmest in January, its coolest month, and 25°C in July, its warmest; the coolest hours of the day run from -4°C to 19°C through the year, and the average temperature over the year is 10°C around the clock. Rain is most likely around April and least likely around August. Every figure here is a decade of observations blended into one representative year, so it reads as what this date is usually like, not a forecast for one particular day.
Sarnia weather in winterDecember to February
High -0°CLow -3°CRain 15%
Winter in Sarnia has typical daily highs of about -0°C and lows of about -3°C, with a 15% chance of rain on a given day.
Sarnia weather in springMarch to May
High 10°CLow 5°CRain 18%
Spring in Sarnia has typical daily highs of about 10°C and lows of about 5°C, with a 18% chance of rain on a given day.
Sarnia weather in summerJune to August
High 24°CLow 18°CRain 14%
Summer in Sarnia has typical daily highs of about 24°C and lows of about 18°C, with a 14% chance of rain on a given day.
Sarnia weather in autumnSeptember to November
High 14°CLow 9°CRain 17%
Autumn in Sarnia has typical daily highs of about 14°C and lows of about 9°C, with a 17% chance of rain on a given day.
When is the rainy season in Sarnia?
Sarnia has no sharply defined rainy season: the chance of rain on a given day runs from 14% in August, the driest month, to 21% in April, the wettest.
What time of year is Sarnia windiest?
Winds in Sarnia are highest in March, averaging 3.4 m/s (12 km/h), and lightest in July, at 2.2 m/s (8 km/h). The prevailing wind is from the W.
What is the average temperature in Sarnia year round?
The average temperature in Sarnia over the whole year is 10°C. July is the hottest month, with highs of about 25°C; January is the coldest, with lows of about -4°C.