Forecast - Environment Canada

Forecast

St. Catharines, ON (Issued: 3:30 PM EDT Monday 14 September 2026)

Tonight

Partly cloudy. Clearing late this evening. Low 13.

Tue, 15 Sep

A mix of sun and cloud. 40 percent chance of showers late in the afternoon. Wind becoming south 20 km/h gusting to 40 in the morning. High 26. Humidex 29. UV index 6 or high.

Night

Cloudy with 40 percent chance of showers and risk of a thunderstorm. Wind southwest 20 km/h gusting to 40 becoming light in the evening. Low 19.

Wed, 16 Sep

Cloudy with 30 percent chance of showers. High 24.

Night

Cloudy periods. Low 16.

Thu, 17 Sep

A mix of sun and cloud with 60 percent chance of showers. High 26.

Night

Cloudy periods. Low 19.

Fri, 18 Sep

Clearing. High 24.

Night

Increasing cloudiness. Low 15.

Sat, 19 Sep

Cloudy. High 20.

Night

Cloudy with 40 percent chance of showers. Low 15.

Sun, 20 Sep

Cloudy with 60 percent chance of showers. High 20.

24 Hour Forecast - St. Catharines, ON

Date/Time	Temp. (°C)	Weather Conditions	LOP †	Wind (km/h)
15 September 2026
12 AM	15	A few clouds	0	SE 10
1 AM	14	Clear	0	SE 10
2 AM	13	Clear	0	SE 10
3 AM	13	Clear	0	SE 10
4 AM	13	Clear	0	SE 10
5 AM	13	Clear	0	S 10
6 AM	14	Mainly cloudy	0	S 10
7 AM	15	A mix of sun and cloud	0	S 10
8 AM	16	A mix of sun and cloud	0	S 20 gust 40
9 AM	17	A mix of sun and cloud	0	S 20 gust 40
10 AM	17	A mix of sun and cloud	0	S 20 gust 40
11 AM	18	A mix of sun and cloud	0	S 20 gust 40
12 PM	20	Mainly sunny	0	S 20 gust 40
1 PM	22	Sunny	20	S 20 gust 40
2 PM	24	Sunny	20	SW 20 gust 40
3 PM	25	Sunny	20	SW 20 gust 40
4 PM	25	Chance of showers	40	SW 20 gust 40
5 PM	26	Chance of showers	40	SW 20 gust 40
6 PM	25	Chance of showers. Risk of thunderstorms	40	SW 20 gust 40
7 PM	25	Chance of showers. Risk of thunderstorms	40	SW 20 gust 40
8 PM	24	Chance of showers. Risk of thunderstorms	40	S 10
9 PM	24	Chance of showers. Risk of thunderstorms	40	S 10
10 PM	23	Chance of showers. Risk of thunderstorms	40	S 10
11 PM	23	Chance of showers. Risk of thunderstorms	40	S 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
	Tue, 15 Sep Chance of showers Max: 26°C	Wed, 16 Sep Chance of showers Max: 24°C	Thu, 17 Sep Chance of showers Max: 26°C	Fri, 18 Sep A mix of sun and cloud Max: 24°C	Sat, 19 Sep Cloudy Max: 20°C	Sun, 20 Sep Chance of showers Max: 20°C
Tonight A few clouds Min: 13°C	Night Chance of showers Min: 19°C	Night Cloudy periods Min: 16°C	Night Cloudy periods Min: 19°C	Night Cloudy Min: 15°C	Night Chance of showers Min: 15°C