Ajax weather in September

In September, Ajax sees average daytime highs of 20°C and overnight lows near 16°C, with 85 mm of rain across 9.1 wet days and about 12.3 hours of daylight. It is the 3rd-warmest and 6th-wettest month of the year here.

Highs ease over the month, from about 22°C in the first days to 18°C by the end. The sky is clear or mostly clear about 37% 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 Ajax's 3rd-clearest and 8th-windiest month. For the whole year in context, see Ajax's year-round climate.

Daytime high
20°
3rd warmest
Overnight low
16°
10th coldest
Rainfall
85 mm
9.1 wet days
Daylight
12 h 18 min
6:02 AM – 6:19 PM
Cloud cover
53%
3rd clearest
Wind
18 km/h
8th windiest
Solar energy
4.15 kWh/m²
Travel score
6.5
out of 10

Ajax is town in Durham Region, Ontario, Canada.

Density
1,786/km²
people per km²

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 22°C in the first days to 18°C by the end.

A typical September day in Ajax reaches about 20°C in the afternoon and slips back to 16°C overnight — a 4°C spread between the day's warmth and the night's chill. On most days the high lands between 16°C and 24°C. Set against its neighbours, September runs about 3°C cooler than August and about 6°C warmer than October.

10°15°20°25°30°151015202530
Avg high (°C)Avg low (°C)
12218
22218
32218
42218
52218
62218
72217
82117
92117
102117
112117
122117
132116
142016
152016
162016
172016
182016
192015
201915
211915
221915
231915
241914
251814
261814
271814
281814
291813
301713

How September really feels in Ajax

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.

Ajax weather by month

How September compares with the rest of the year at a glance. September is the 3rd-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° / -6°8612.59.79.10.0
Feb-1° / -7°6196.910.20.0
Mar / -3°7010.14.711.60.0
Apr / 96111.613.20.7
May12° / 7810.1014.53.0
Jun18° / 14°769.7015.25.7
Jul23° / 19°678.9014.97.0
Aug23° / 19°678.8013.87.2
Sep20° / 16°859.1012.36.5
Oct14° / 10°9512.10.110.83.8
Nov / 9211.42.29.51.0
Dec / -2°8712.66.88.80.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 37% 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 46%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16040
25941
35842
45842
55842
65743
75743
85644
95644
105545
115545
125545
135446
145446
155446
165347
175347
185347
195347
205347
215347
225248
235248
245248
255050
265050
275149
285050
295050
305050

Chance of precipitation in September

Any precipitation

Ajax gets around 85 mm of rain over 9.1 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 30% and peaks near 37% on the wettest days. The odds climb toward the end of the month.

0%10%20%30%40%50%151015202530
Rain chance (%)
127
227
328
428
529
629
730
830
931
1031
1131
1230
1330
1430
1530
1629
1729
1829
1929
2029
2129
2230
2330
2431
2532
2633
2734
2835
2936
3037

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 44% of days. Sticky, muggy-or-worse air turns up on roughly 13% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1232624234
2242623224
3262723214
4272722204
5292721193
6302721193
7322721183
8332721172
9342721162
10362721152
11372721141
12382621141
13402621131
14412521121
15422521110
16442521100
17452421100
1846242190
1948242080
2049232080
2151231970
2252231870
2355221760
2457221650
2558221550
2660211450
2762211340
2863211240
2965201140
3068191030

Wind in September

Winds average 18 km/h in September.

Across September, daily wind ranges from about 16 km/h on the calmest days to 20 km/h at its breeziest. It stays fairly steady from day to day.

0510152025151015202530
Wind speed (km/h)Feels
116light breeze
217light breeze
317light breeze
417light breeze
517light breeze
617light breeze
717light breeze
817light breeze
917light breeze
1017light breeze
1117light breeze
1218light breeze
1318light breeze
1418light breeze
1518light breeze
1618light breeze
1718light breeze
1818light breeze
1918light breeze
2018light breeze
2118light breeze
2219light breeze
2319light breeze
2419light breeze
2519light breeze
2619light breeze
2719light breeze
2819light breeze
2919light breeze
3020light 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 5:44 AM to 6:18 AM, and sunset from 6:48 PM to 5:53 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.15:446:48
213.05:456:46
313.05:466:44
412.95:486:42
512.95:496:40
612.85:506:38
712.85:516:37
812.75:526:35
912.75:536:33
1012.65:556:31
1112.65:566:29
1212.55:576:27
1312.55:586:25
1412.45:596:23
1512.36:006:21
1612.36:026:19
1712.26:036:17
1812.26:046:16
1912.16:056:14
2012.16:066:12
2112.06:076:10
2212.06:096:08
2311.96:106:06
2411.96:116:04
2511.86:126:02
2611.86:136:00
2711.76:155:58
2811.76:165:56
2911.66:175:55
3011.66:185:53

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.15 kWh/m².

For context, solar energy here swings from a low near 1.28 kWh/m² to a high of 6.32 kWh/m² in June across the year — September's 4.15 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.8Bright
24.7Bright
34.7Bright
44.7Bright
54.6Bright
64.6Bright
74.5Bright
84.5Bright
94.4Bright
104.4Bright
114.3Bright
124.3Bright
134.3Bright
144.2Bright
154.2Bright
164.1Bright
174.1Bright
184.0Bright
194.0Bright
204.0Moderate
213.9Moderate
223.9Moderate
233.8Moderate
243.8Moderate
253.7Moderate
263.6Moderate
273.6Moderate
283.5Moderate
293.5Moderate
303.4Moderate
Planning a trip in September

Is September a good time to visit Ajax?

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

6.5
Sightseeing
3rd-best month of the year
3.4
Beach & pool
3rd-best month of the year

September is a reasonable time to visit Ajax for sightseeing.

What to pack for Ajax in September

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

In September, Ajax sees daytime highs around 20°C and nights near 16°C. Worth packing: rain gear. About 9 days see rain.

rain gear

Sea temperature near Ajax 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 13 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 Ajax 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 Ajax peaks around June 21 at about 8 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 21 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 21UV 1
UV index (midday)Level
Jan1Low
Feb2Low
Mar4Moderate
Apr5High
May6High
Jun8Very high
Jul8Very high
Aug6High
Sep5High
Oct3Moderate
Nov2Low
Dec1Low

Air quality in Ajax 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 Ajax is worst in May — around 21 µg/m³ PM2.5 (moderate), about 2.2× the cleanest month (November, 10 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodMay 2021 µg/m³Nov 2310 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb14Moderate
Mar17Moderate
Apr18Moderate
May21Moderate
Jun20Moderate
Jul20Moderate
Aug17Moderate
Sep16Moderate
Oct11Good
Nov10Good
Dec10Good
Location & terrain

Where is Ajax?

Ajax sits at 43.9°N, 79.0°W, 97 m above sea level, in Canada. The nearest listed city is Whitby, 9.0 km away.

Topography around Ajax

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

Within 3 km, the terrain around Ajax has only modest variations in elevation — a maximum elevation change of 62 m around an average of 95 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 215 m; within 80 km, significant variations in elevation — a maximum elevation change of 484 m.

The land around Ajax is covered by artificial surfaces (53%) and trees (28%) within 3 km, water (35%) and trees (23%) within 16 km, and water (39%) and trees (24%) within 80 km.

3 km
62 m
16 km
215 m
80 km
484 m
treesgrasslandcroplandartificial surfacesbare terrainwaterwetland
September weather nearby: Whitby 9.0 km · Pickering 10 km · Rouge 12 km · Brooklin 13 km · West Hill 15 km · Morningside 16 km · Oshawa 16 km · Malvern 16 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 Ajax (43.8501°, -79.0329°, elevation 97 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).