Bolton weather in May

In May, Bolton sees average daytime highs of 18°C and overnight lows near 7°C, with 81 mm of rain across 11.3 wet days and about 14.5 hours of daylight. It is the 5th-warmest and 3rd-wettest month of the year here.

Highs climb over the month, from about 16°C in the first days to 21°C by the end. The sky is clear or mostly clear about 26% of the time in May, and the air most often feels dry.

Daylight stretches from about 13 h 54 min at the start of May to 15 hours by month's end. Set against the rest of the year, May is Bolton's 5th-clearest and 8th-windiest month. For the whole year in context, see Bolton's year-round climate.

Daytime high
18°
5th warmest
Overnight low
8th coldest
Rainfall
81 mm
11.3 wet days
Daylight
14 h 30 min
4:59 AM – 7:31 PM
Cloud cover
63%
5th clearest
Wind
12 km/h
8th windiest
Solar energy
5.92 kWh/m²
Travel score
5.6
out of 10

Bolton is town in Caledon, Ontario, Canada.

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

Temperature in May

Average highAverage lowShaded bands: 10–90% of days

Highs climb over the month, from about 16°C in the first days to 21°C by the end.

A typical May day in Bolton reaches about 18°C in the afternoon and slips back to 7°C overnight — a 11°C spread between the day's warmth and the night's chill. On most days the high lands between 11°C and 26°C. Set against its neighbours, May runs about 7°C warmer than April and about 5°C cooler than June.

10°20°30°151015202531
Avg high (°C)Avg low (°C)
1154
2155
3165
4165
5165
6165
7166
8176
9176
10176
11176
12176
13186
14187
15187
16187
17187
18197
19198
20198
21198
22208
23208
24209
25209
26209
27209
282110
292110
302110
312110

How May really feels in Bolton

Once humidity and wind are folded in, May 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

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

Bolton weather by month

How May compares with the rest of the year at a glance. May is the 5th-warmest and 3rd-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan-2° / -10°569.68.79.10.0
Feb-1° / -10°477.97.210.20.0
Mar / -5°55105.611.60.3
Apr12° / 76112.613.22.8
May18° / 8111.3014.55.6
Jun23° / 12°8811.5015.26.5
Jul26° / 15°8311014.96.6
Aug25° / 14°799.7013.86.9
Sep21° / 10°729.5012.36.5
Oct13° / 73110.410.83.6
Nov / -1°6710.23.59.50.7
Dec / -6°5710.288.80.0

Cloud cover in May

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 26% of the time in May.

Beyond those clear spells, partly cloudy skies cover about 17% of May, with mostly cloudy or overcast conditions the remaining 57%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
13961
23961
33961
43961
54060
64060
73961
84060
94159
104159
114159
124258
134258
144357
154357
164357
174357
184357
194456
204456
214456
224555
234555
244555
254555
264555
274555
284654
294654
304555
314555

Chance of precipitation in May

Any precipitation

Bolton gets around 81 mm of rain over 11.3 wet days in May. 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 38% on the wettest days.

0%10%20%30%40%50%151015202531
Rain chance (%)
137
236
336
436
536
636
736
836
936
1036
1135
1235
1335
1435
1535
1635
1735
1835
1935
2035
2135
2236
2336
2436
2537
2637
2737
2838
2938
3038
3138

Humidity in May

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, May lands in the dry band about 89% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)
197210
297210
396310
496310
596310
695410
795410
895410
995410
1093520
1193520
1293520
1393520
1493520
1592620
1691630
1791630
1890730
1989740
2087850
2186851
2284961
2384961
24821071
25821071
26801181
27791182
28771292
29771292
30761392
317513102

Wind in May

Winds average 12 km/h in May.

Across May, 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
112light breeze
212light breeze
312light breeze
412light breeze
512light breeze
612calm
712calm
812calm
912calm
1012calm
1112calm
1212calm
1312calm
1412calm
1512calm
1612calm
1712calm
1812calm
1912calm
2012calm
2112calm
2212calm
2312calm
2412calm
2512calm
2612calm
2711calm
2811calm
2911calm
3011calm
3111calm

Sunrise & sunset in May

DaylightNight

Daylight runs from about 13 h 54 min at the start of May to 15 hours by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 66 minutes over May. Sunrise moves from 5:19 AM to 4:46 AM, and sunset from 7:14 PM to 7:46 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
113.95:197:14
214.05:177:15
314.05:167:16
414.15:147:17
514.15:137:19
614.15:117:20
714.25:107:21
814.25:097:22
914.35:077:23
1014.35:067:24
1114.35:057:26
1214.45:047:27
1314.45:037:28
1414.55:017:29
1514.55:007:30
1614.54:597:31
1714.64:587:32
1814.64:577:33
1914.64:567:35
2014.74:557:36
2114.74:547:37
2214.74:537:38
2314.84:527:39
2414.84:517:40
2514.84:517:41
2614.94:507:42
2714.94:497:43
2814.94:487:44
2914.94:487:45
3015.04:477:45
3115.04:467:46

Solar energy in May

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in May, about 5.92 kWh/m².

For context, solar energy here swings from a low near 1.27 kWh/m² to a high of 6.31 kWh/m² in June across the year — May's 5.92 kWh/m² sits near the top of that range.

0246151015202531
Solar energy (kWh/m²)Level
15.5Bright
25.5Bright
35.6Bright
45.6Bright
55.7Bright
65.7Bright
75.7Bright
85.7Bright
95.8Bright
105.8Bright
115.8Bright
125.8Bright
135.9Bright
145.9Bright
155.9Bright
165.9Bright
176.0Bright
186.0Bright
196.0Intense
206.0Intense
216.0Intense
226.1Intense
236.1Intense
246.1Intense
256.1Intense
266.1Intense
276.1Intense
286.1Intense
296.1Intense
306.1Intense
316.1Intense
Planning a trip in May

Is May a good time to visit Bolton?

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

5.6
Sightseeing
5th-best month of the year
2.1
Beach & pool
5th-best month of the year

May is a reasonable time to visit Bolton for sightseeing.

What to pack for Bolton in May

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

In May, Bolton sees daytime highs around 18°C and nights near 7°C. Worth packing: a warm layer, rain gear and sun protection. About 11 days see rain.

a warm layerrain gearsun protection

Sea temperature near Bolton in May

The nearest coast averages about 7°C in May — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 41 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 20 to Sep 2 — about 1.5 months when the water holds above 20°C.

0°10°20°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarm
Sea temperature (°C)Comfort
Jan4Bracing
Feb3Bracing
Mar3Bracing
Apr4Bracing
May7Bracing
Jun15Bracing
Jul20Cool
Aug21Refreshing
Sep19Cool
Oct13Bracing
Nov8Bracing
Dec5Bracing

UV index in Bolton in May

LowModerateHighVery highExtreme

Clear-sky midday UV in May peaks around 6 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Bolton peaks around June 22 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 8 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJun 22UV 8Dec 21UV 1
UV index (midday)Level
Jan1Low
Feb2Low
Mar4Moderate
Apr5High
May6High
Jun8Very high
Jul8Very high
Aug6High
Sep5High
Oct3Moderate
Nov2Low
Dec1Low

Air quality in Bolton in May

GoodModeratePoorUnhealthyVery unhealthy

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

Air quality in Bolton 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 Bolton?

Bolton sits at 43.9°N, 79.7°W, 221 m above sea level, in Canada. The nearest listed city is Mount Olive-Silverstone-Jamestown, 19 km away.

Topography around Bolton

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

Within 3 km, the terrain around Bolton has only modest variations in elevation — a maximum elevation change of 83 m around an average of 249 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 323 m; within 80 km, significant variations in elevation — a maximum elevation change of 473 m.

The land around Bolton is covered by trees (37%) and artificial surfaces (29%) within 3 km, trees (35%), cropland (27%) and grassland (25%) within 16 km, and trees (30%), cropland (29%) and water (21%) within 80 km.

3 km
83 m
16 km
323 m
80 km
473 m
treesgrasslandcroplandartificial surfacesbare terrainwater
May weather nearby: Mount Olive-Silverstone-Jamestown 19 km · Vaughan 20 km · Caledon 21 km · Humbermede 21 km · West Humber-Clairville 21 km · Black Creek 22 km · Brampton 22 km · Glenfield-Jane Heights 23 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 Bolton (43.8795°, -79.7379°, elevation 221 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).