Forecast - Environment Canada

Forecast

St. Catharines, ON (Issued: 5:00 AM EDT Saturday 23 August 2025)

Today

A mix of sun and cloud. Wind becoming southwest 30 km/h gusting to 50 this morning. High 28. Humidex 35. UV index 8 or very high.

Tonight

Partly cloudy. 40 percent chance of showers this evening and after midnight. Risk of a thunderstorm this evening. Wind southwest 30 km/h gusting to 50 becoming light late this evening. Low 19.

Sun, 24 Aug

Becoming a mix of sun and cloud in the morning. 30 percent chance of showers in the afternoon. Wind becoming southwest 20 km/h in the morning. High 26. Humidex 31. UV index 7 or high.

Night

Cloudy periods with 30 percent chance of showers. Low 15.

Mon, 25 Aug

A mix of sun and cloud with 30 percent chance of showers. High 20.

Night

Cloudy periods with 30 percent chance of showers. Low 12.

Tue, 26 Aug

A mix of sun and cloud with 30 percent chance of showers. High 20.

Night

Clear. Low 11.

Wed, 27 Aug

Sunny. High 21.

Night

Clear. Low 14.

Thu, 28 Aug

Sunny. High 23.

Night

Clear. Low 15.

Fri, 29 Aug

Sunny. High 24.

24 Hour Forecast - St. Catharines, ON

Date/Time	Temp. (°C)	Weather Conditions	LOP †	Wind (km/h)
23 August 2025
6 AM	18	A few clouds	0	S 5
7 AM	20	Mainly sunny	0	S 5
8 AM	21	Mainly sunny	0	S 5
9 AM	22	A mix of sun and cloud	0	S 20
10 AM	22	A mix of sun and cloud	0	S 20
11 AM	23	A mix of sun and cloud	0	S 20
12 PM	25	A mix of sun and cloud	0	SW 30 gust 50
1 PM	26	A mix of sun and cloud	0	SW 30 gust 50
2 PM	28	A mix of sun and cloud	0	SW 30 gust 50
3 PM	28	A mix of sun and cloud	20	SW 30 gust 50
4 PM	27	A mix of sun and cloud	20	SW 30 gust 50
5 PM	27	A mix of sun and cloud	20	SW 30 gust 50
6 PM	26	Chance of showers. Risk of thunderstorms	40	SW 30 gust 50
7 PM	25	Chance of showers. Risk of thunderstorms	40	SW 30 gust 50
8 PM	24	Chance of showers. Risk of thunderstorms	40	SW 20
9 PM	24	Chance of showers. Risk of thunderstorms	40	SW 20
10 PM	23	Chance of showers. Risk of thunderstorms	40	SW 20
11 PM	23	Chance of showers. Risk of thunderstorms	40	W 15
24 August 2025
12 AM	22	Chance of showers	40	W 15
1 AM	21	Chance of showers	40	W 15
2 AM	20	Chance of showers	40	W 15
3 AM	20	Partly cloudy	20	W 15
4 AM	20	Mainly cloudy	20	W 15
5 AM	20	Mainly cloudy	20	W 15

† Likelihood of Precipitation (LOP) as described in the public forecast as a chance of measurable precipitation for a period of time. Nil: 0% Low: 40% or below Medium: 60% or 70% High: Above 70%

Extended Forecast - Environment Canada
Today A mix of sun and cloud Max: 28°C	Sun, 24 Aug Chance of showers Max: 26°C	Mon, 25 Aug Chance of showers Max: 20°C	Tue, 26 Aug Chance of showers Max: 20°C	Wed, 27 Aug Sunny Max: 21°C	Thu, 28 Aug Sunny Max: 23°C	Fri, 29 Aug Sunny Max: 24°C
Tonight Chance of showers Min: 19°C	Night Chance of showers Min: 15°C	Night Chance of showers Min: 12°C	Night Clear Min: 11°C	Night Clear Min: 14°C	Night Clear Min: 15°C