Grimsby weather in September

In September, Grimsby sees average daytime highs of 21°C and overnight lows near 16°C, with 78 mm of rain across 9.3 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 6th-wettest month of the year here.

Highs ease over the month, from about 23°C in the first days to 18°C by the end. The sky is clear or mostly clear about 35% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 hours at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Grimsby's 3rd-clearest and 8th-windiest month. For the whole year in context, see Grimsby's year-round climate.

Daytime high
21°
4th warmest
Overnight low
16°
9th coldest
Rainfall
78 mm
9.3 wet days
Daylight
12 h 18 min
6:04 AM – 6:21 PM
Cloud cover
55%
3rd clearest
Wind
14 km/h
8th windiest
Solar energy
4.13 kWh/m²
Travel score
6.6
out of 10

Grimsby is town in Niagara Region, Ontario, Canada.

Density
398/km²
people per km²
Founded
1790

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

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 23°C in the first days to 18°C by the end.

A typical September day in Grimsby reaches about 21°C in the afternoon and slips back to 16°C overnight — a 5°C spread between the day's warmth and the night's chill. On most days the high lands between 16°C and 25°C. Set against its neighbours, September runs about 4°C cooler than August and about 6°C warmer than October.

10°15°20°25°30°151015202530
Avg high (°C)Avg low (°C)
12318
22318
32318
42318
52318
62317
72217
82217
92217
102217
112217
122216
132116
142116
152116
162116
172115
182115
192015
202015
212015
222014
232014
241914
251914
261914
271913
281813
291813
301813

How September really feels in Grimsby

Once humidity and wind are folded in, September 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

September sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Grimsby weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 6th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan-0° / -5°7311.58.59.20.0
Feb-0° / -6°588.66.610.20.0
Mar / -2°719.94.511.60.1
Apr / 9511.41.813.11.7
May15° / 8010.8014.44.4
Jun21° / 16°8210.8015.16.4
Jul25° / 19°749.7014.97.0
Aug24° / 19°679.7013.87.1
Sep21° / 16°789.3012.36.6
Oct14° / 8811.3010.84.1
Nov / 8110.61.99.51.4
Dec / -1°7511.15.88.90.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 35% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 18% of September, with mostly cloudy or overcast conditions the remaining 47%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15743
25743
35743
45644
55644
65644
75644
85545
95545
105545
115446
125446
135347
145446
155446
165347
175347
185347
195347
205149
215149
225149
235050
245050
254951
264951
274951
284852
294852
304753

Chance of precipitation in September

Any precipitation

Grimsby gets around 78 mm of rain over 9.3 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 31% and peaks near 38% on the wettest days. The odds climb toward the end of the month.

0%10%20%30%40%50%151015202530
Rain chance (%)
129
229
329
429
530
630
730
830
930
1029
1129
1229
1329
1429
1529
1629
1729
1829
1929
2030
2130
2231
2332
2433
2535
2636
2737
2837
2938
3038

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the dry band about 41% of days. Sticky, muggy-or-worse air turns up on roughly 14% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1192527245
2202527235
3222626224
4232625224
5252625214
6262624203
7282624193
8302723182
9312623182
10332623172
11342623162
12362622151
13372622141
14392622131
15402621121
16422621111
17432621101
1844262091
1946261980
2047261880
2149261870
2250261770
2352261660
2454261550
2554261550
2656261440
2758251340
2861241230
2961241230
3063231130

Wind in September

Winds average 14 km/h in September.

Across September, daily wind ranges from about 13 km/h on the calmest days to 15 km/h at its breeziest. It stays fairly steady from day to day.

05101520151015202530
Wind speed (km/h)Feels
113light breeze
213light breeze
313light breeze
413light breeze
513light breeze
613light breeze
713light breeze
813light breeze
914light breeze
1014light breeze
1114light breeze
1214light breeze
1314light breeze
1414light breeze
1514light breeze
1614light breeze
1714light breeze
1814light breeze
1914light breeze
2014light breeze
2114light breeze
2215light breeze
2315light breeze
2415light breeze
2515light breeze
2615light breeze
2715light breeze
2815light breeze
2915light breeze
3015light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 hours at the start of September to 11 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 84 minutes over September. Sunrise moves from 5:47 AM to 6:20 AM, and sunset from 6:49 PM to 5:55 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:476:49
213.05:486:47
312.95:496:45
412.95:506:44
512.85:516:42
612.85:536:40
712.75:546:38
812.75:556:36
912.65:566:34
1012.65:576:33
1112.55:586:31
1212.55:596:29
1312.46:006:27
1412.46:026:25
1512.36:036:23
1612.36:046:21
1712.26:056:19
1812.26:066:18
1912.16:076:16
2012.16:086:14
2112.06:106:12
2212.06:116:10
2311.96:126:08
2411.96:136:06
2511.86:146:04
2611.86:156:03
2711.76:176:01
2811.76:185:59
2911.66:195:57
3011.66:205:55

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.13 kWh/m².

For context, solar energy here swings from a low near 1.29 kWh/m² to a high of 6.29 kWh/m² in June across the year — September's 4.13 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.7Bright
24.7Bright
34.7Bright
44.6Bright
54.6Bright
64.5Bright
74.5Bright
84.4Bright
94.4Bright
104.3Bright
114.3Bright
124.3Bright
134.2Bright
144.2Bright
154.2Bright
164.1Bright
174.1Bright
184.0Bright
194.0Moderate
204.0Moderate
213.9Moderate
223.9Moderate
233.8Moderate
243.8Moderate
253.7Moderate
263.6Moderate
273.6Moderate
283.5Moderate
293.5Moderate
303.5Moderate
Planning a trip in September

Is September a good time to visit Grimsby?

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

6.6
Sightseeing
3rd-best month of the year
3.9
Beach & pool
4th-best month of the year

September is a reasonable time to visit Grimsby for sightseeing.

What to pack for Grimsby in September

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

In September, Grimsby sees daytime highs around 21°C and nights near 16°C. Worth packing: rain gear. About 9 days see rain.

rain gear

Sea temperature near Grimsby in September

The nearest coast averages about 19°C in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 20 km away) is warmest in August at about 21°C and coldest in February near 3°C.

It's comfortable for a long swim from Jul 22 to Sep 1 — about 1.4 months when the water holds above 20°C.

0°10°20°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarm
Sea temperature (°C)Comfort
Jan4Bracing
Feb3Bracing
Mar3Bracing
Apr4Bracing
May8Bracing
Jun15Cool
Jul20Cool
Aug21Refreshing
Sep19Cool
Oct13Bracing
Nov8Bracing
Dec5Bracing

UV index in Grimsby in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 5 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Grimsby peaks around June 20 at about 8 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 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 8Dec 22UV 1
UV index (midday)Level
Jan1Low
Feb2Moderate
Mar4Moderate
Apr5High
May6High
Jun8Very high
Jul8Very high
Aug6High
Sep5High
Oct3Moderate
Nov2Low
Dec1Low

Air quality in Grimsby in September

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where September falls, not just the annual average.

Air quality in Grimsby is worst in May — around 22 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (December, 10 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodMay 2021 µg/m³Dec 1010 µg/m³
PM2.5 (µg/m³)Level
Jan12Good
Feb15Moderate
Mar18Moderate
Apr18Moderate
May22Moderate
Jun20Moderate
Jul20Moderate
Aug17Moderate
Sep17Moderate
Oct11Good
Nov10Good
Dec10Good
Location & terrain

Where is Grimsby?

Grimsby sits at 43.2°N, 79.6°W, 88 m above sea level, in Canada. The nearest listed city is Stoney Creek, 16 km away.

Topography around Grimsby

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Grimsby.

Within 3 km, the terrain around Grimsby has only modest variations in elevation — a maximum elevation change of 145 m around an average of 110 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 155 m; within 80 km, significant variations in elevation — a maximum elevation change of 401 m.

The land around Grimsby is covered by water (41%) and trees (23%) within 3 km, water (45%) and cropland (23%) within 16 km, and water (38%), trees (21%) and cropland (21%) within 80 km.

3 km
145 m
16 km
155 m
80 km
401 m
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Stoney Creek 16 km · Hamilton 24 km · St. Catharines 26 km · Oakville 29 km · Waterdown 30 km · Burlington 30 km · Thorold 31 km · Ancaster 34 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 Grimsby (43.2001°, -79.5663°, elevation 88 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. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).