Sarnia weather in July

In July, Sarnia sees average daytime highs of 26°C and overnight lows near 18°C, with 71 mm of rain across 11 wet days and about 14.8 hours of daylight. It is the 1st-warmest and 6th-wettest month of the year here.

Day-to-day highs hold fairly steady near 26°C through the month. The sky is clear or mostly clear about 34% of the time in July, and the air most often feels humid.

Daylight stretches from about 15 h 06 min at the start of July to 14 h 24 min by month's end. Set against the rest of the year, July is Sarnia's 1st-clearest and 11th-windiest month. For the whole year in context, see Sarnia's year-round climate.

Daytime high
26°
1st warmest
Overnight low
18°
12th coldest
Rainfall
71 mm
11 wet days
Daylight
14 h 54 min
5:09 AM – 8:02 PM
Cloud cover
54%
1st clearest
Wind
11 km/h
11th windiest
Solar energy
6.23 kWh/m²
Travel score
6.6
out of 10

Sarnia is city in Ontario, Canada.

Air quality
Good
PM2.5 7 µg/m³ · 2019
Density
440/km²
people per km²
Founded
1830

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in July

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 26°C through the month.

A typical July day in Sarnia reaches about 26°C in the afternoon and slips back to 18°C overnight — a 8°C spread between the day's warmth and the night's chill. On most days the high lands between 22°C and 30°C. Set against its neighbours, July runs about 2°C warmer than June and about 1°C warmer than August.

10°15°20°25°30°35°151015202531
Avg high (°C)Avg low (°C)
12618
22618
32618
42618
52618
62618
72618
82618
92618
102618
112618
122618
132619
142619
152619
162619
172619
182619
192619
202619
212619
222619
232619
242619
252619
262619
272619
282619
292619
302619
312619

How July really feels in Sarnia

Once humidity and wind are folded in, July averages 0 days that feel above 32°C and 0 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C
0
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

July 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 July compares with the rest of the year at a glance. July is the 1st-warmest and 6th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan-1° / -7°579.67.39.20.0
Feb / -7°518.46.310.20.0
Mar / -3°579.64.611.60.3
Apr11° / 8511.41.813.12.7
May18° / 10°8512014.45.4
Jun24° / 16°8710.8015.16.7
Jul26° / 18°7111014.86.6
Aug25° / 18°7010.4013.86.9
Sep21° / 14°739.1012.36.7
Oct15° / 7710.80.110.84.3
Nov / 669.72.49.51.2
Dec / -3°569.45.68.90.0

Cloud cover in July

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 34% of the time in July, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 21% of July, with mostly cloudy or overcast conditions the remaining 45%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
15743
25743
35743
45743
55743
65743
75743
85842
95743
105644
115644
125644
135545
145545
155545
165347
175347
185248
195347
205347
215248
225248
235347
245347
255446
265446
275545
285545
295644
305644
315743

Chance of precipitation in July

Any precipitation

Sarnia gets around 71 mm of rain over 11 wet days in July. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 36% and peaks near 39% on the wettest days.

0%10%20%30%40%50%151015202531
Rain chance (%)
136
236
335
435
534
634
733
833
933
1033
1134
1234
1334
1435
1535
1636
1736
1837
1937
2038
2138
2238
2338
2439
2539
2638
2738
2838
2938
3037
3137

Humidity in July

DryComfortableHumidMuggyOppressiveMiserable

Most of July feels humid — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, July lands in the humid band about 29% of days. Sticky, muggy-or-worse air turns up on roughly 35% of them.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1202623265
2202623265
3192624256
4182724256
5172725256
6172725257
7162626257
8152627257
9142527258
10142528268
11132429268
12122329278
13122330279
14112230279
15112231289
16102231289
17102231289
18102131289
191021312810
201021312910
211021312910
22921312910
23921312810
2492231289
2592231289
2692331289
2792431289
2892430279
2992530278
3092530278
3192530278

Wind in July

Winds average 11 km/h in July.

Across July, daily wind ranges from about 11 km/h on the calmest days to 12 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202531
Wind speed (km/h)Feels
112calm
212calm
312calm
412calm
512calm
612calm
712calm
812calm
912calm
1011calm
1111calm
1211calm
1311calm
1411calm
1511calm
1611calm
1711calm
1811calm
1911calm
2011calm
2111calm
2211calm
2311calm
2411calm
2511calm
2611calm
2711calm
2811calm
2911calm
3011calm
3111calm

Sunrise & sunset in July

DaylightNight

Daylight runs from about 15 h 06 min at the start of July to 14 h 24 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 42 minutes over July. Sunrise moves from 4:59 AM to 5:23 AM, and sunset from 8:07 PM to 7:48 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
115.14:598:07
215.14:598:07
315.15:008:07
415.15:008:07
515.15:018:06
615.15:028:06
715.15:028:06
815.05:038:06
915.05:048:05
1015.05:048:05
1115.05:058:04
1215.05:068:04
1314.95:068:03
1414.95:078:03
1514.95:088:02
1614.95:098:02
1714.95:108:01
1814.85:118:00
1914.85:118:00
2014.85:127:59
2114.75:137:58
2214.75:147:57
2314.75:157:56
2414.75:167:55
2514.65:177:54
2614.65:187:54
2714.65:197:53
2814.55:207:52
2914.55:217:50
3014.55:227:49
3114.45:237:48

Solar energy in July

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in July, about 6.23 kWh/m².

For context, solar energy here swings from a low near 1.36 kWh/m² to a high of 6.37 kWh/m² in June across the year — July's 6.23 kWh/m² sits near the top of that range.

0246151015202531
Solar energy (kWh/m²)Level
16.5Intense
26.5Intense
36.5Intense
46.5Intense
56.5Intense
66.5Intense
76.4Intense
86.4Intense
96.4Intense
106.4Intense
116.4Intense
126.3Intense
136.3Intense
146.3Intense
156.3Intense
166.2Intense
176.2Intense
186.2Intense
196.1Intense
206.1Intense
216.1Intense
226.0Intense
236.0Intense
246.0Intense
256.0Bright
266.0Bright
275.9Bright
285.9Bright
295.9Bright
305.8Bright
315.8Bright
Planning a trip in July

Is July a good time to visit Sarnia?

Our two travel scores rate July for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

6.6
Sightseeing
4th-best month of the year
6.3
Beach & pool
1st-best month of the year

July is a reasonable time to visit Sarnia for sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Sarnia in July

From July's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In July, Sarnia sees daytime highs around 26°C and nights near 18°C. Pack sun protection. Worth having: light clothes and rain gear. About 11 days see rain.

sun protectionlight clothesrain gear

Sea temperature near Sarnia in July

The nearest coast averages about 20°C in July — 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.

0°10°20°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmcomfortable to swim
Sea temperature (°C)Comfort
Jan2Bracing
Feb1Bracing
Mar1Bracing
Apr3Bracing
May7Bracing
Jun14Bracing
Jul20Refreshing
Aug22Refreshing
Sep20Cool
Oct14Bracing
Nov9Bracing
Dec5Bracing

UV index in Sarnia in July

LowModerateHighVery highExtreme

Clear-sky midday UV in July peaks 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.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJun 20UV 9Dec 20UV 1
UV index (midday)Level
Jan2Low
Feb2Moderate
Mar4Moderate
Apr5High
May7High
Jun9Very high
Jul8Very high
Aug7High
Sep6High
Oct3Moderate
Nov2Moderate
Dec1Low
Location & terrain

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.

3 km
19 m
16 km
69 m
80 km
216 m
treesgrasslandcroplandartificial surfacesbare terrainwaterwetland
July weather nearby: Port Huron 2.0 km · Mount Clemens 57 km · Clinton Township 61 km · Shelby 62 km · Strathroy 64 km · Chatham 65 km · Saint Clair Shores 67 km · Sterling Heights 68 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
Christian 53%none 35%Muslim 5%Hindu 2%

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. Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).