St. Catharines weather in May

In May, St. Catharines sees average daytime highs of 15°C and overnight lows near 10°C, with 83 mm of rain across 11.4 wet days and about 14.4 hours of daylight. It is the 5th-warmest and 6th-wettest month of the year here.

Highs climb over the month, from about 12°C in the first days to 18°C by the end. The sky is clear or mostly clear about 28% 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 14 h 54 min by month's end. Set against the rest of the year, May is St. Catharines's 5th-clearest and 9th-windiest month. For the whole year in context, see St. Catharines's year-round climate.

Daytime high
15°
5th warmest
Overnight low
10°
8th coldest
Rainfall
83 mm
11.4 wet days
Daylight
14 h 30 min
4:59 AM – 7:27 PM
Cloud cover
61%
5th clearest
Wind
13 km/h
9th windiest
Solar energy
5.93 kWh/m²
Travel score
4.5
out of 10

St. Catharines is city in Ontario, Canada.

Air quality
Good
PM2.5 7 µg/m³ · 2019
Density
1,410/km²
people per km²
Founded
1783

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 12°C in the first days to 18°C by the end.

A typical May day in St. Catharines reaches about 15°C in the afternoon and slips back to 10°C overnight — a 6°C spread between the day's warmth and the night's chill. On most days the high lands between 11°C and 20°C. Set against its neighbours, May runs about 6°C warmer than April and about 6°C cooler than June.

10°15°20°25°151015202531
Avg high (°C)Avg low (°C)
1127
2127
3127
4137
5137
6138
7138
8138
9148
10148
11148
12149
13149
14159
15159
16159
171510
181610
191610
201610
211610
221611
231711
241711
251711
261712
271812
281812
291812
301813
311813

How May really feels in St. Catharines

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.

St. Catharines weather by month

How May compares with the rest of the year at a glance. May is the 5th-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°7511.999.20.0
Feb-0° / -6°599710.20.0
Mar / -2°7310.44.611.60.1
Apr / 9711.71.813.11.8
May15° / 10°8311.4014.44.5
Jun21° / 16°9111.1015.16.4
Jul25° / 20°8810.8014.96.9
Aug24° / 19°759.9013.87.1
Sep21° / 16°859.8012.36.5
Oct14° / 9212.10.110.84.1
Nov / 8210.829.51.3
Dec / -1°7711.66.68.90.0

Cloud cover in May

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 28% of the time in May.

Beyond those clear spells, partly cloudy skies cover about 16% of May, with mostly cloudy or overcast conditions the remaining 56%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
14258
24357
34357
44258
54357
64357
74258
84258
94357
104258
114258
124357
134357
144258
154258
164357
174456
184456
194555
204555
214555
224555
234654
244753
254753
264753
274753
284852
294852
304753
314753

Chance of precipitation in May

Any precipitation

St. Catharines gets around 83 mm of rain over 11.4 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 37% and peaks near 39% on the wettest days.

0%10%20%30%40%50%151015202531
Rain chance (%)
138
238
338
438
539
639
739
839
939
1039
1139
1238
1338
1438
1538
1637
1737
1836
1936
2035
2135
2234
2334
2434
2534
2634
2734
2834
2934
3034
3134

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 88% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)
199100
299100
398200
498200
598200
698200
797300
897300
997300
1096400
1196400
1295500
1395500
1494600
1592710
1691810
1791810
1889920
19881020
20861130
21851230
22821341
23801451
24791461
25771571
26761671
27751681
28731791
29721891
307018102
316819112

Wind in May

Winds average 13 km/h in May.

Across May, daily wind ranges from about 13 km/h on the calmest days to 14 km/h at its breeziest. It stays fairly steady from day to day.

05101520151015202531
Wind speed (km/h)Feels
114light breeze
214light breeze
314light breeze
414light breeze
513light breeze
613light breeze
713light breeze
813light breeze
913light breeze
1013light breeze
1113light breeze
1213light breeze
1313light breeze
1413light breeze
1513light breeze
1613light breeze
1713light breeze
1813light breeze
1913light breeze
2013light breeze
2113light breeze
2213light breeze
2313light breeze
2413light breeze
2513light breeze
2613light breeze
2713light breeze
2813light breeze
2913light breeze
3013light breeze
3113light breeze

Sunrise & sunset in May

DaylightNight

Daylight runs from about 13 h 54 min at the start of May to 14 h 54 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 60 minutes over May. Sunrise moves from 5:18 AM to 4:47 AM, and sunset from 7:10 PM to 7:42 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
113.95:187:10
213.95:177:12
314.05:157:13
414.05:147:14
514.05:127:15
614.15:117:16
714.15:107:17
814.25:087:18
914.25:077:20
1014.25:067:21
1114.35:057:22
1214.35:047:23
1314.45:027:24
1414.45:017:25
1514.45:007:26
1614.54:597:27
1714.54:587:28
1814.54:577:30
1914.64:567:31
2014.64:557:32
2114.64:547:33
2214.74:537:34
2314.74:527:35
2414.74:527:36
2514.84:517:37
2614.84:507:38
2714.84:497:38
2814.84:497:39
2914.94:487:40
3014.94:477:41
3114.94:477:42

Solar energy in May

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in May, about 5.93 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 — May's 5.93 kWh/m² sits near the top of that range.

0246151015202531
Solar energy (kWh/m²)Level
15.5Bright
25.5Bright
35.6Bright
45.6Bright
55.6Bright
65.7Bright
75.7Bright
85.7Bright
95.7Bright
105.8Bright
115.8Bright
125.8Bright
135.8Bright
145.8Bright
155.9Bright
165.9Bright
175.9Bright
186.0Bright
196.0Bright
206.0Intense
216.0Intense
226.1Intense
236.1Intense
246.1Intense
256.1Intense
266.2Intense
276.2Intense
286.2Intense
296.2Intense
306.2Intense
316.2Intense
Planning a trip in May

Is May a good time to visit St. Catharines?

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

4.5
Sightseeing
5th-best month of the year
0.6
Beach & pool
5th-best month of the year

May is a reasonable time to visit St. Catharines for sightseeing.

What to pack for St. Catharines in May

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

In May, St. Catharines sees daytime highs around 15°C and nights near 10°C. Worth packing: a warm layer, rain gear and sun protection. About 11 days see rain.

a warm layerrain gearsun protection

Sea temperature near St. Catharines 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 25 km away) is warmest in August at about 22°C and coldest in February near 3°C.

It's comfortable for a long swim from Jul 17 to Sep 6 — about 1.7 months when the water holds above 20°C.

0°10°20°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmcomfortable to swim
Sea temperature (°C)Comfort
Jan4Bracing
Feb3Bracing
Mar3Bracing
Apr4Bracing
May7Bracing
Jun15Bracing
Jul20Refreshing
Aug22Refreshing
Sep19Cool
Oct13Bracing
Nov8Bracing
Dec5Bracing

UV index in St. Catharines 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 St. Catharines peaks around June 19 at about 8 (very high) — sunscreen and a hat are worth it in the middle of the day. 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 19UV 8Dec 21UV 1
UV index (midday)Level
Jan1Low
Feb2Moderate
Mar4Moderate
Apr5High
May6High
Jun8Very high
Jul7Very high
Aug6High
Sep5High
Oct3Moderate
Nov2Low
Dec1Low
Location & terrain

Where is St. Catharines?

St. Catharines sits at 43.2°N, 79.2°W, 102 m above sea level, in Canada. The nearest listed city is Thorold, 7.0 km away.

Topography around St. Catharines

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

Within 3 km, the terrain around St. Catharines has only modest variations in elevation — a maximum elevation change of 47 m around an average of 100 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 193 m; within 80 km, significant variations in elevation — a maximum elevation change of 483 m.

The land around St. Catharines is covered by artificial surfaces (51%) and trees (33%) within 3 km, water (33%) and trees (20%) within 16 km, and water (41%) and trees (24%) within 80 km.

3 km
47 m
16 km
193 m
80 km
483 m
treesgrasslandcroplandartificial surfaceswater
May weather nearby: Thorold 7.0 km · Niagara-on-the-Lake 16 km · Niagara Falls 16 km · Niagara Falls 17 km · Welland 21 km · Grimsby 26 km · Grand Island 27 km · Port Colborne 30 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 St. Catharines (43.1713°, -79.2427°, elevation 102 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).