Sarnia in Fall
In fall (September, October and November), Sarnia sees average daytime highs around 15°C and overnight lows near 8°C, with 216 mm of precipitation over about 30 wet days across the season. It is the 2nd-warmest season and the 3rd-wettest season.
Over the season highs ease from about 24°C in early September to 5°C by late November. The sky is clear or mostly clear about 25% of the time across fall, and the air most often feels dry.
Fall is Sarnia's 2nd-best season to visit on our travel score. For the whole year in context, see Sarnia's year-round climate.
- Avg daytime high
- 15°C
- 2nd-warmest season
- Avg overnight low
- 8°C
- Precipitation
- 216 mm
- 30 wet days
- Avg wind
- 15 km/h
- Travel score
- 4.1
- 2nd-best season
- Months
- Sep · Oct · Nov
Temperature in Sarnia in Fall
Over the season highs ease from about 24°C in early September to 5°C by late November.
A typical fall day in Sarnia reaches about 15°C and drops to 8°C overnight. The warmest of the three months is September, the coolest November.
How fall really feels in Sarnia
Once humidity and wind are folded in, fall brings about 0 days that feel above 32°C and 25 that feel at or below 0°C.
The story in fall is cold — wind chill drags the overnight "feels like" below the raw low.
Sarnia weather by month
How the three fall months (September, October and November) 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 Fall
The sky is clear or mostly clear about 25% of the time across fall.
Chance of precipitation in Fall
Sarnia gets around 216 mm of rain and snow over 30 wet days across fall. The line is the day-by-day chance of measurable precipitation.
Humidity in Fall
Most of fall feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Fall
Winds average 15 km/h across fall.
Sunrise & sunset in Fall
Daylight runs from about 13 hours in early September to 9 h 06 min by late November. The lit band spans sunrise to sunset each day.
Solar energy in Fall
Average shortwave solar energy reaching the ground each day across fall, about 2.9 kWh/m².
Is fall a good time to visit Sarnia?
Our two travel scores rate fall for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
fall is a reasonable time to visit Sarnia for sightseeing.
What to pack for Sarnia in Fall
From fall's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In fall, Sarnia sees daytime highs around 15°C and nights near 8°C. Pack a warm layer. Worth having: a heavy coat and rain gear. About 30 days see rain.
Sea temperature near Sarnia in Fall
The nearest coast averages about 14°C across fall — 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 Fall
Clear-sky midday UV across fall averages around 4 — enough to warrant sun protection. 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.