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September weather forecast in Thunder Bay

30 days Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

30 days Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Sun

Sunday

Mon

Monday

Tue

Tuesday

Wed

Wednesday

Thu

Thursday

Fri

Friday

Sat

Saturday

31 August, sun

	730 mmHg		76%
	4.5 m/s		+16

31 August, Sunday. day, 22°; night, 12°; clear

1 September, mon

	730 mmHg		75%
	4.69 m/s		+16

1 September, Monday. day, 22°; night, 12°; clear

2 September, tue

	729 mmHg		77%
	4.69 m/s		+16

2 September, Tuesday. day, 22°; night, 12°; partly cloudy

3 September, wed

	729 mmHg		77%
	4.69 m/s		+15

3 September, Wednesday. day, 22°; night, 11°; rain

4 September, thu

	731 mmHg		77%
	4.3 m/s		+14

4 September, Thursday. day, 21°; night, 10°; clear

5 September, fri

	730 mmHg		79%
	4.5 m/s		+15

5 September, Friday. day, 21°; night, 11°; partly cloudy

6 September, sat

	729 mmHg		79%
	4.8 m/s		+15

6 September, Saturday. day, 21°; night, 11°; rain

7 September, sun

	729 mmHg		78%
	4.9 m/s		+15

7 September, Sunday. day, 19°; night, 10°; clear

8 September, mon

	730 mmHg		78%
	4.19 m/s		+15

8 September, Monday. day, 19°; night, 9°; clear

9 September, tue

	731 mmHg		79%
	3.8 m/s		+14

9 September, Tuesday. day, 18°; night, 8°; clear

10 September, wed

	731 mmHg		80%
	4.3 m/s		+15

10 September, Wednesday. day, 19°; night, 9°; partly cloudy

11 September, thu

	730 mmHg		77%
	4.5 m/s		+14

11 September, Thursday. day, 20°; night, 10°; clear

12 September, fri

	730 mmHg		76%
	4.6 m/s		+14

12 September, Friday. day, 19°; night, 9°; partly cloudy

13 September, sat

	729 mmHg		78%
	4.6 m/s		+14

13 September, Saturday. day, 18°; night, 9°; overcast

14 September, sun

	730 mmHg		78%
	4.8 m/s		+13

14 September, Sunday. day, 17°; night, 8°; partly cloudy

15 September, mon

	732 mmHg		79%
	4.4 m/s		+13

15 September, Monday. day, 17°; night, 7°; partly cloudy

16 September, tue

	730 mmHg		80%
	4.5 m/s		+13

16 September, Tuesday. day, 18°; night, 8°; partly cloudy

17 September, wed

	730 mmHg		80%
	4.69 m/s		+12

17 September, Wednesday. day, 18°; night, 9°; rain

18 September, thu

	730 mmHg		78%
	4.3 m/s		+13

18 September, Thursday. day, 18°; night, 8°; overcast

19 September, fri

	728 mmHg		82%
	4.9 m/s		+13

19 September, Friday. day, 18°; night, 9°; rain

20 September, sat

	728 mmHg		78%
	5.1 m/s		+13

20 September, Saturday. day, 18°; night, 9°; overcast

21 September, sun

	728 mmHg		78%
	5.2 m/s		+13

21 September, Sunday. day, 17°; night, 8°; rain

22 September, mon

	730 mmHg		78%
	4.69 m/s		+13

22 September, Monday. day, 16°; night, 8°; overcast

23 September, tue

	731 mmHg		79%
	4.3 m/s		+13

23 September, Tuesday. day, 15°; night, 6°; partly cloudy

24 September, wed

	729 mmHg		79%
	5 m/s		+12

24 September, Wednesday. day, 16°; night, 7°; overcast

25 September, thu

	729 mmHg		81%
	4.5 m/s		+12

25 September, Thursday. day, 16°; night, 7°; rain

26 September, fri

	728 mmHg		82%
	4.3 m/s		+13

26 September, Friday. day, 16°; night, 7°; rain

27 September, sat

	727 mmHg		80%
	4.69 m/s		+12

27 September, Saturday. day, 16°; night, 7°; rain

28 September, sun

	729 mmHg		79%
	4.6 m/s		+11

28 September, Sunday. day, 15°; night, 6°; clear

29 September, mon

	730 mmHg		79%
	4.9 m/s		+11

29 September, Monday. day, 14°; night, 5°; rain

30 September, tue

	729 mmHg		80%
	4.6 m/s		+11

30 September, Tuesday. day, 14°; night, 5°; rain

1 October, wed

	730 mmHg		80%
	4.8 m/s		+11

1 October, Wednesday. day, 13°; night, 5°; clear

2 October, thu

	730 mmHg		77%
	5 m/s		+11

2 October, Thursday. day, 13°; night, 5°; clear

3 October, fri

	730 mmHg		79%
	4.69 m/s		+11

3 October, Friday. day, 13°; night, 5°; rain

4 October, sat

	731 mmHg		76%
	4.8 m/s		+11

4 October, Saturday. day, 13°; night, 4°; clear

Average data for 10 years

Thunder Bay September

7

sunny days

10

days with precipitation

8

cloudy days

7 sunny days; 10 days with precipitation; 8 cloudy days;

79

%

air humidity

3.2

m/s

WindSW

86

mm of precipitation

(12% of annual average)

+13

°C

Water temperature

air humidity 79%; 86 millimeters of precipitation (12% of annual average); Wind south-westerly 3.2 Meters per second; Water temperature +13°

Weather graphs for September

TemperatureWater temperaturePrecipitation chance, %Humidity, %Wind, m/sPressure, mmHg

SW

SW

SW

SW

SW

SW

SW

S

S

S

SW

SW

SW

SW

SW

SW

SW

S

S

SW

SW

SW

S

S

SW

SW

SW

SW

SW

SW

1

Average data for 10 years

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

Daytime temperature

Night-time temperature

Cities near you

Duluth
Hayward
Dryden
Minocqua
Cloquet
Spooner
Marshfield
Stevens Point
Ashland

Cities with similar weather in September

Helsinki
Riga
Tallinn
Stockholm
Oslo
Yurmala
Palanga
Dublin
Copenhagen

The weather forecast for September 2025 is based on historical data from the past 10 years.

In September, the weather in Thunder Bay is typically warm. Average daily high temperature in September is about 18 degrees above zero. On average, Thunder Bay has 10 rainy, 8 partly cloudy, 7 sunny, and 5 cloudy days in September. The rains are usually heavy.

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