Sarnia in Summer
In summer (June, July and August), Sarnia sees average daytime highs around 25°C and overnight lows near 17°C, with 228 mm of rain over about 32 wet days across the season. It is the warmest season of the year and the wettest season of the year.
Over the season highs climb from about 22°C in early June to 24°C by late August. The sky is clear or mostly clear about 33% of the time across summer, and the air most often feels humid.
Summer is Sarnia's best season of the year to visit on our travel score. For the whole year in context, see Sarnia's year-round climate.
- Avg daytime high
- 25°C
- warmest season of the year
- Avg overnight low
- 17°C
- Rainfall
- 228 mm
- 32 wet days
- Avg wind
- 12 km/h
- Travel score
- 6.7
- best season of the year
- Months
- Jun · Jul · Aug
Temperature in Sarnia in Summer
Over the season highs climb from about 22°C in early June to 24°C by late August.
A typical summer day in Sarnia reaches about 25°C and drops to 17°C overnight. The warmest of the three months is July, the coolest June.
How summer really feels in Sarnia
Once humidity and wind are folded in, summer brings about 0 days that feel above 32°C and 0 that feel at or below 0°C.
summer sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.
Sarnia weather by month
How the three summer months (June, July and August) compare with the rest of the year — the season's months are highlighted.
| Month | High / Low (°C) | Rainfall (mm) | Wet days | Snow days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|---|
| Jan | -1° / -7° | 57 | 9.6 | 7.3 | 9.2 | 0.0 |
| Feb | 0° / -7° | 51 | 8.4 | 6.3 | 10.2 | 0.0 |
| Mar | 5° / -3° | 57 | 9.6 | 4.6 | 11.6 | 0.3 |
| Apr | 11° / 3° | 85 | 11.4 | 1.8 | 13.1 | 2.7 |
| May | 18° / 10° | 85 | 12 | 0 | 14.4 | 5.4 |
| Jun | 24° / 16° | 87 | 10.8 | 0 | 15.1 | 6.7 |
| Jul | 26° / 18° | 71 | 11 | 0 | 14.8 | 6.6 |
| Aug | 25° / 18° | 70 | 10.4 | 0 | 13.8 | 6.9 |
| Sep | 21° / 14° | 73 | 9.1 | 0 | 12.3 | 6.7 |
| Oct | 15° / 8° | 77 | 10.8 | 0.1 | 10.8 | 4.3 |
| Nov | 8° / 2° | 66 | 9.7 | 2.4 | 9.5 | 1.2 |
| Dec | 2° / -3° | 56 | 9.4 | 5.6 | 8.9 | 0.0 |
Cloud cover in Summer
The sky is clear or mostly clear about 33% of the time across summer.
Chance of precipitation in Summer
Sarnia gets around 228 mm of rain over 32 wet days across summer. The line is the day-by-day chance of measurable precipitation.
Humidity in Summer
Most of summer feels humid — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Summer
Winds average 12 km/h across summer.
Sunrise & sunset in Summer
Daylight runs from about 14 h 54 min in early June to 13 h 06 min by late August. The lit band spans sunrise to sunset each day.
Solar energy in Summer
Average shortwave solar energy reaching the ground each day across summer, about 6.0 kWh/m².
Is summer a good time to visit Sarnia?
Our two travel scores rate summer for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
summer is a reasonable time to visit Sarnia for sightseeing.
What to pack for Sarnia in Summer
From summer's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In summer, Sarnia sees daytime highs around 25°C and nights near 17°C. Pack sun protection. Worth having: light clothes and rain gear. About 32 days see rain.
Sea temperature near Sarnia in Summer
The nearest coast averages about 19°C across summer — the other half of the beach question. The full-year curve and swim-comfort zones are below.
The sea at the nearest coast (about 16 km away) is warmest in August at about 22°C and coldest in February near 1°C.
It's comfortable for a long swim from Jul 19 to Sep 8 — about 1.7 months when the water holds above 20°C.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°C) | 2 | 1 | 1 | 3 | 7 | 14 | 20 | 22 | 20 | 14 | 9 | 5 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Refreshing | Refreshing | Cool | Bracing | Bracing | Bracing |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 2 | Bracing |
| Feb | 1 | Bracing |
| Mar | 1 | Bracing |
| Apr | 3 | Bracing |
| May | 7 | Bracing |
| Jun | 14 | Bracing |
| Jul | 20 | Refreshing |
| Aug | 22 | Refreshing |
| Sep | 20 | Cool |
| Oct | 14 | Bracing |
| Nov | 9 | Bracing |
| Dec | 5 | Bracing |
UV index in Sarnia in Summer
Clear-sky midday UV across summer averages around 8 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in Sarnia peaks around June 20 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 20 at about 1 (low).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 2 | 2 | 4 | 5 | 7 | 9 | 8 | 7 | 6 | 3 | 2 | 1 |
| Level | Low | Moderate | Moderate | High | High | Very high | Very high | High | High | Moderate | Moderate | Low |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 2 | Low |
| Feb | 2 | Moderate |
| Mar | 4 | Moderate |
| Apr | 5 | High |
| May | 7 | High |
| Jun | 9 | Very high |
| Jul | 8 | Very high |
| Aug | 7 | High |
| Sep | 6 | High |
| Oct | 3 | Moderate |
| Nov | 2 | Moderate |
| Dec | 1 | Low |
Where is Sarnia?
Sarnia sits at 43.0°N, 82.4°W, 185 m above sea level, in Canada. The nearest listed city is Port Huron, 2.0 km away.
Topography around Sarnia
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Sarnia.
Within 3 km, the terrain around Sarnia has only modest variations in elevation — a maximum elevation change of 19 m around an average of 182 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 69 m; within 80 km, only modest variations in elevation — a maximum elevation change of 216 m.
The land around Sarnia is covered by artificial surfaces (52%) and trees (22%) within 3 km, cropland (27%), trees (25%) and water (24%) within 16 km, and cropland (45%) and water (25%) within 80 km.
Canada travel facts
- Travel advisory
- Level 1
- Exercise Normal Precautions
- Power plugs
- Type A / B
- 120 V · 60 Hz
- Prices
- ≈ 83% of US
- price level, 2025
- GDP per capita
- $55,698
- 2025
- Happiness
- 6.7 / 10
- World Happiness, 2025
- Safe drinking water
- 97%
- of population, 2024
- Homicide rate
- 2
- per 100k, 2023
- Road deaths
- 5.3
- per 100k/yr, 2019
- Income group
- High
- World Bank
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Sarnia (42.9787°, -82.4041°, elevation 185 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google.