Keswick weather in September

In September, Keswick sees average daytime highs of 21°C and overnight lows near 11°C, with 72 mm of rain across 9.6 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 7th-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 31% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 h 06 min at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Keswick's 3rd-clearest and 10th-windiest month. For the whole year in context, see Keswick's year-round climate.

Daytime high
21°
4th warmest
Overnight low
11°
9th coldest
Rainfall
72 mm
9.6 wet days
Daylight
12 h 18 min
6:03 AM – 6:21 PM
Cloud cover
58%
3rd clearest
Wind
12 km/h
10th windiest
Solar energy
4.03 kWh/m²
Travel score
6.5
out of 10

Keswick is human settlement in Georgina, Ontario, Canada.

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 Keswick reaches about 21°C in the afternoon and slips back to 11°C overnight — a 10°C spread between the day's warmth and the night's chill. On most days the high lands between 15°C and 27°C. Set against its neighbours, September runs about 4°C cooler than August and about 7°C warmer than October.

10°20°30°151015202530
Avg high (°C)Avg low (°C)
12314
22314
32313
42313
52313
62313
72213
82213
92212
102212
112212
122212
132112
142111
152111
162111
172111
182011
192010
202010
212010
221910
231910
24199
25199
26189
27189
28189
29188
30178

How September really feels in Keswick

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.

Keswick weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 7th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan-3° / -11°5810.610.19.10.0
Feb-2° / -11°478.47.710.20.0
Mar / -5°569.96.111.60.1
Apr11° / 7610.82.613.22.7
May18° / 8010.8014.55.6
Jun23° / 13°8410.6015.36.7
Jul26° / 16°7810.80156.7
Aug25° / 15°759.6013.87.0
Sep21° / 11°729.6012.36.5
Oct13° / 7611.70.410.83.6
Nov / -1°6810.73.99.40.6
Dec / -6°5710.78.68.70.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 31% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 17% of September, with mostly cloudy or overcast conditions the remaining 52%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15446
25347
35347
45347
55347
65248
75149
85149
95149
105050
114951
124951
134951
144852
154852
164852
174753
184753
194753
204753
214654
224654
234555
244555
254456
264456
274258
284258
294159
304258

Chance of precipitation in September

Any precipitation

Keswick gets around 72 mm of rain over 9.6 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 32% and peaks near 36% on the wettest days.

0%10%20%30%40%50%151015202530
Rain chance (%)
129
229
330
430
531
631
731
832
932
1032
1132
1232
1332
1431
1531
1631
1731
1831
1931
2031
2131
2232
2332
2433
2533
2634
2735
2835
2936
3036

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 61% of days. Sticky, muggy-or-worse air turns up on roughly 5% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1382921121
2392820111
3412819110
4432719100
5452718100
647271790
749261790
850261680
952251580
1053251570
1155241470
1256241460
1358231360
1459231350
1561221250
1662221240
1763211240
1864211140
1966201130
2067191130
2168191030
2270181020
237118920
247217920
257516810
267516810
277715710
287814710
298013610
308013610

Wind in September

Winds average 12 km/h in September.

Across September, 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.

051015151015202530
Wind speed (km/h)Feels
111calm
211calm
311calm
411calm
511calm
611calm
711calm
811calm
911calm
1011calm
1111calm
1211calm
1312calm
1412calm
1512calm
1612calm
1712calm
1812calm
1912calm
2012calm
2112calm
2212calm
2312light breeze
2412light breeze
2512light breeze
2612light breeze
2712light breeze
2812light breeze
2912light breeze
3012light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 06 min 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 90 minutes over September. Sunrise moves from 5:45 AM to 6:20 AM, and sunset from 6:50 PM to 5:54 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.15:456:50
213.05:466:48
313.05:486:46
412.95:496:44
512.95:506:42
612.85:516:40
712.85:526:39
812.75:546:37
912.75:556:35
1012.65:566:33
1112.65:576:31
1212.55:586:29
1312.56:006:27
1412.46:016:25
1512.46:026:23
1612.36:036:21
1712.26:046:19
1812.26:066:17
1912.16:076:15
2012.16:086:13
2112.06:096:12
2212.06:106:10
2311.96:126:08
2411.96:136:06
2511.86:146:04
2611.86:156:02
2711.76:166:00
2811.76:185:58
2911.66:195:56
3011.66:205:54

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.03 kWh/m².

For context, solar energy here swings from a low near 1.28 kWh/m² to a high of 6.25 kWh/m² in June across the year — September's 4.03 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.7Bright
24.6Bright
34.6Bright
44.5Bright
54.5Bright
64.5Bright
74.4Bright
84.4Bright
94.3Bright
104.3Bright
114.2Bright
124.2Bright
134.1Bright
144.1Bright
154.1Bright
164.0Bright
174.0Moderate
183.9Moderate
193.9Moderate
203.8Moderate
213.8Moderate
223.7Moderate
233.7Moderate
243.6Moderate
253.6Moderate
263.5Moderate
273.5Moderate
283.4Moderate
293.4Moderate
303.3Moderate
Planning a trip in September

Is September a good time to visit Keswick?

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

6.5
Sightseeing
4th-best month of the year
3.7
Beach & pool
4th-best month of the year

September is a reasonable time to visit Keswick for sightseeing.

What to pack for Keswick in September

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

In September, Keswick sees daytime highs around 21°C and nights near 11°C. Worth packing: rain gear. About 10 days see rain.

rain gear

Sea temperature near Keswick 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 63 km away) is warmest in August at about 21°C and coldest in March near 3°C.

It's comfortable for a long swim from Jul 27 to Sep 2 — about 1.2 months when the water holds above 20°C.

0°10°20°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarm
Sea temperature (°C)Comfort
Jan4Bracing
Feb3Bracing
Mar3Bracing
Apr4Bracing
May7Bracing
Jun14Bracing
Jul19Cool
Aug21Refreshing
Sep19Cool
Oct13Bracing
Nov8Bracing
Dec5Bracing

UV index in Keswick 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 Keswick peaks around June 21 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 7 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJun 21UV 8Dec 22UV 1
UV index (midday)Level
Jan1Low
Feb2Low
Mar3Moderate
Apr5High
May6High
Jun8Very high
Jul8Very high
Aug6High
Sep5High
Oct3Moderate
Nov2Low
Dec1Low

Air quality in Keswick 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 Keswick is worst in May — around 19 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (November, 9 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodMay 2019 µg/m³Nov 239 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb14Moderate
Mar16Moderate
Apr17Moderate
May19Moderate
Jun18Moderate
Jul18Moderate
Aug16Moderate
Sep14Moderate
Oct10Good
Nov9Good
Dec9Good
Location & terrain

Where is Keswick?

Keswick sits at 44.3°N, 79.5°W, 230 m above sea level, in Canada. The nearest listed city is Innisfil, 16 km away.

Topography around Keswick

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

Within 3 km, the terrain around Keswick has only modest variations in elevation — a maximum elevation change of 59 m around an average of 234 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 126 m; within 80 km, significant variations in elevation — a maximum elevation change of 532 m.

The land around Keswick is covered by cropland (29%), trees (25%) and water (24%) within 3 km, trees (34%), cropland (27%) and water (22%) within 16 km, and trees (41%) and cropland (23%) within 80 km.

3 km
59 m
16 km
126 m
80 km
532 m
treesgrasslandcroplandartificial surfaceswaterwetland
September weather nearby: Innisfil 16 km · East Gwillimbury 17 km · Newmarket 22 km · Barrie 23 km · Aurora 28 km · Whitchurch-Stouffville 30 km · Uxbridge 33 km · Alliston 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 Keswick (44.2501°, -79.4663°, elevation 230 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).