Thunder Bay weather in April

In April, Thunder Bay sees average daytime highs of 6°C and overnight lows near -3°C, with 54 mm of precipitation across 8.3 wet days and about 13.4 hours of daylight. It is the 7th-warmest and 7th-wettest month of the year here.

Highs climb over the month, from about 3°C in the first days to 9°C by the end. The sky is clear or mostly clear about 25% of the time in April, and the air most often feels dry.

Daylight stretches from about 12 h 30 min at the start of April to 14 h 12 min by month's end. Set against the rest of the year, April is Thunder Bay's 8th-clearest and 7th-windiest month. For the whole year in context, see Thunder Bay's year-round climate.

Daytime high: 6°; 7th warmest
Overnight low: -3°; 6th coldest
Precipitation: 54 mm; 8.3 wet days
Daylight: 13 h 24 min; 6:15 AM – 7:40 PM
Cloud cover: 65%; 8th clearest
Wind: 12 km/h; 7th windiest
Solar energy: 5.29 kWh/m²
Travel score: 0.7; out of 10

Thunder Bay is city in Thunder Bay District, Ontario, Canada.

Air quality: Excellent; PM2.5 5 µg/m³ · 2019
Density: 243/km²; people per km²
Founded: 1683

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

← March Thunder Bay year-round climate May →Best places to visit in April

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

Temperature in April

Average highAverage lowShaded bands: 10–90% of days

Highs climb over the month, from about 3°C in the first days to 9°C by the end.

A typical April day in Thunder Bay reaches about 6°C in the afternoon and slips back to -3°C overnight — a 9°C spread between the day's warmth and the night's chill. On most days the high lands between 0°C and 12°C. Set against its neighbours, April runs about 7°C warmer than March and about 7°C cooler than May.

	1	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
Avg high (°C)	3	3	3	4	4	4	4	4	5	5	5	5	6	6	6	6	7	7	7	7	7	8	8	8	8	8	9	9	9	9
Avg low (°C)	-6	-6	-5	-5	-5	-5	-5	-4	-4	-4	-4	-3	-3	-3	-3	-3	-2	-2	-2	-2	-2	-1	-1	-1	-1	-1	0	0	0	0

	Avg high (°C)	Avg low (°C)
1	3	-6
2	3	-6
3	3	-5
4	4	-5
5	4	-5
6	4	-5
7	4	-5
8	4	-4
9	5	-4
10	5	-4
11	5	-4
12	5	-3
13	6	-3
14	6	-3
15	6	-3
16	6	-3
17	7	-2
18	7	-2
19	7	-2
20	7	-2
21	7	-2
22	8	-1
23	8	-1
24	8	-1
25	8	-1
26	8	-1
27	9	0
28	9	0
29	9	0
30	9	0

How April really feels in Thunder Bay

Once humidity and wind are folded in, April averages 0 days that feel above 32°C and 30 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C

heat index over the day's high

Days feeling ≤ 0°C

4 feel bitter (≤ -10°C)

The story in April is cold — wind chill drags the overnight "feels like" below the raw low.

Thunder Bay weather by month

How April compares with the rest of the year at a glance. April is the 7th-warmest and 7th-wettest month here — the current month is highlighted below.

Month	High / Low (°C)	Rainfall (mm)	Wet days	Snow days	Daylight (hours)	Travel score
Jan	-10° / -18°	29	6.5	7.5	8.6	0.0
Feb	-7° / -16°	22	4.9	5.4	9.9	0.0
Mar	-1° / -10°	31	6.8	5.6	11.6	0.0
Apr	6° / -3°	54	8.3	5	13.4	0.7
May	13° / 4°	66	10.1	0.8	15	3.5
Jun	19° / 10°	65	10.5	0	15.8	5.8
Jul	22° / 14°	76	10.6	0	15.5	6.6
Aug	22° / 13°	67	9.1	0	14.1	6.7
Sep	17° / 9°	84	10.5	0	12.4	5.2
Oct	9° / 3°	72	10.4	1.3	10.6	1.7
Nov	1° / -5°	49	7.8	5.7	9	0.0
Dec	-6° / -13°	38	7.3	7.8	8.2	0.0

Cloud cover in April

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 25% of the time in April.

Beyond those clear spells, partly cloudy skies cover about 13% of April, with mostly cloudy or overcast conditions the remaining 62%. Skies tend to open up as the month goes on.

	1	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
Clearer (%)	34	34	34	34	34	35	35	35	35	36	36	38	38	39	39	39	39	41	41	40	41	41	41	41	41	41	41	41	41	40
Cloudier (%)	66	66	66	66	66	65	65	65	65	64	64	62	62	61	61	61	61	59	59	60	59	59	59	59	59	59	59	59	59	60

	Clearer (%)	Cloudier (%)
1	34	66
2	34	66
3	34	66
4	34	66
5	34	66
6	35	65
7	35	65
8	35	65
9	35	65
10	36	64
11	36	64
12	38	62
13	38	62
14	39	61
15	39	61
16	39	61
17	39	61
18	41	59
19	41	59
20	40	60
21	41	59
22	41	59
23	41	59
24	41	59
25	41	59
26	41	59
27	41	59
28	41	59
29	41	59
30	40	60

Chance of precipitation in April

Any precipitationSnow

Thunder Bay gets around 54 mm of rain and snow over 8.3 wet days in April. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable precipitation averages around 28% and peaks near 29% on the wettest days, and about 5 days bring snow.

	1	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
Rain chance (%)	28	28	28	28	28	28	28	28	27	27	27	27	27	27	27	27	27	27	27	27	27	27	28	28	28	28	28	28	29	29
Snow chance (%)	21	21	21	21	21	21	21	20	20	19	19	18	18	17	17	16	16	15	15	15	14	14	13	12	12	11	11	10	9	9

	Rain chance (%)	Snow chance (%)
1	28	21
2	28	21
3	28	21
4	28	21
5	28	21
6	28	21
7	28	21
8	28	20
9	27	20
10	27	19
11	27	19
12	27	18
13	27	18
14	27	17
15	27	17
16	27	16
17	27	16
18	27	15
19	27	15
20	27	15
21	27	14
22	27	14
23	28	13
24	28	12
25	28	12
26	28	11
27	28	11
28	28	10
29	29	9
30	29	9

Humidity in April

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, April lands in the dry band about 100% of days. It rarely turns muggy — the humid and sticky bands barely register.

	1	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
Dry (%)	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100

Wind in April

Winds average 12 km/h in April.

Across April, 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.

	1	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
Wind speed (km/h)	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	11	11	11
Feels	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm

	Wind speed (km/h)	Feels
1	12	calm
2	12	calm
3	12	calm
4	12	calm
5	12	calm
6	12	calm
7	12	calm
8	12	calm
9	12	calm
10	12	calm
11	12	calm
12	12	calm
13	12	calm
14	12	calm
15	12	calm
16	12	calm
17	12	calm
18	12	calm
19	12	calm
20	12	calm
21	12	calm
22	12	calm
23	12	calm
24	12	calm
25	12	calm
26	12	calm
27	12	calm
28	11	calm
29	11	calm
30	11	calm

Sunrise & sunset in April

DaylightNight

Daylight runs from about 12 h 30 min at the start of April to 14 h 12 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 102 minutes over April. Sunrise moves from 6:46 AM to 5:48 AM, and sunset from 7:18 PM to 8:00 PM.

	1	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
Daylight (h)	12.5	12.6	12.6	12.7	12.8	12.8	12.9	12.9	13.0	13.1	13.1	13.2	13.2	13.3	13.4	13.4	13.5	13.5	13.6	13.6	13.7	13.8	13.8	13.9	13.9	14.0	14.0	14.1	14.1	14.2
Sunrise (AM)	6:46	6:44	6:42	6:39	6:37	6:35	6:33	6:31	6:29	6:27	6:25	6:23	6:21	6:19	6:17	6:15	6:13	6:11	6:09	6:07	6:05	6:03	6:01	5:59	5:57	5:55	5:54	5:52	5:50	5:48
Sunset (PM)	7:18	7:19	7:20	7:22	7:23	7:25	7:26	7:28	7:29	7:31	7:32	7:34	7:35	7:37	7:38	7:40	7:41	7:43	7:44	7:46	7:47	7:49	7:50	7:52	7:53	7:55	7:56	7:58	7:59	8:00

	Daylight (h)	Sunrise (AM)	Sunset (PM)
1	12.5	6:46	7:18
2	12.6	6:44	7:19
3	12.6	6:42	7:20
4	12.7	6:39	7:22
5	12.8	6:37	7:23
6	12.8	6:35	7:25
7	12.9	6:33	7:26
8	12.9	6:31	7:28
9	13.0	6:29	7:29
10	13.1	6:27	7:31
11	13.1	6:25	7:32
12	13.2	6:23	7:34
13	13.2	6:21	7:35
14	13.3	6:19	7:37
15	13.4	6:17	7:38
16	13.4	6:15	7:40
17	13.5	6:13	7:41
18	13.5	6:11	7:43
19	13.6	6:09	7:44
20	13.6	6:07	7:46
21	13.7	6:05	7:47
22	13.8	6:03	7:49
23	13.8	6:01	7:50
24	13.9	5:59	7:52
25	13.9	5:57	7:53
26	14.0	5:55	7:55
27	14.0	5:54	7:56
28	14.1	5:52	7:58
29	14.1	5:50	7:59
30	14.2	5:48	8:00

Solar energy in April

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in April, about 5.29 kWh/m².

For context, solar energy here swings from a low near 1.12 kWh/m² to a high of 6.21 kWh/m² in June across the year — April's 5.29 kWh/m² falls in the middle.

	1	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
Solar energy (kWh/m²)	4.7	4.8	4.8	4.8	4.9	4.9	5.0	5.0	5.1	5.1	5.1	5.2	5.2	5.2	5.3	5.3	5.3	5.4	5.4	5.4	5.5	5.5	5.5	5.5	5.5	5.6	5.6	5.6	5.6	5.7
Level	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright

	Solar energy (kWh/m²)	Level
1	4.7	Bright
2	4.8	Bright
3	4.8	Bright
4	4.8	Bright
5	4.9	Bright
6	4.9	Bright
7	5.0	Bright
8	5.0	Bright
9	5.1	Bright
10	5.1	Bright
11	5.1	Bright
12	5.2	Bright
13	5.2	Bright
14	5.2	Bright
15	5.3	Bright
16	5.3	Bright
17	5.3	Bright
18	5.4	Bright
19	5.4	Bright
20	5.4	Bright
21	5.5	Bright
22	5.5	Bright
23	5.5	Bright
24	5.5	Bright
25	5.5	Bright
26	5.6	Bright
27	5.6	Bright
28	5.6	Bright
29	5.6	Bright
30	5.7	Bright

Planning a trip in April

Is April a good time to visit Thunder Bay?

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

0.7

Sightseeing

7th-best month of the year

0.0

Beach & pool

7th-best month of the year

April is a weaker month for outdoor sightseeing in Thunder Bay.

What to pack for Thunder Bay in April

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

In April, Thunder Bay sees daytime highs around 6°C and nights near -3°C. Pack a warm layer and a heavy coat. Worth having: rain gear and sun protection. About 8 days see rain.

a warm layera heavy coatrain gearsun protection

Sea temperature near Thunder Bay in April

The nearest coast averages about 2°C in April — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea offshore is warmest in August at about 15°C and coldest in March near 1°C.

The water stays below 20°C all year — cool enough that most swimmers want a wetsuit.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Sea temperature (°C)	2	1	1	2	3	4	9	15	14	10	6	4
Comfort	Bracing	Bracing	Bracing	Bracing	Bracing	Bracing	Bracing	Cool	Bracing	Bracing	Bracing	Bracing

	Sea temperature (°C)	Comfort
Jan	2	Bracing
Feb	1	Bracing
Mar	1	Bracing
Apr	2	Bracing
May	3	Bracing
Jun	4	Bracing
Jul	9	Bracing
Aug	15	Cool
Sep	14	Bracing
Oct	10	Bracing
Nov	6	Bracing
Dec	4	Bracing

UV index in Thunder Bay in April

LowModerateHighVery highExtreme

Clear-sky midday UV in April peaks around 5 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Thunder Bay peaks around June 17 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 6 months of the year.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
UV index (midday)	1	2	3	5	6	8	6	6	5	3	1	1
Level	Low	Low	Moderate	Moderate	High	Very high	High	High	Moderate	Moderate	Low	Low

	UV index (midday)	Level
Jan	1	Low
Feb	2	Low
Mar	3	Moderate
Apr	5	Moderate
May	6	High
Jun	8	Very high
Jul	6	High
Aug	6	High
Sep	5	Moderate
Oct	3	Moderate
Nov	1	Low
Dec	1	Low

Location & terrain

Where is Thunder Bay?

Thunder Bay sits at 48.4°N, 89.3°W, 188 m above sea level, in Canada. The nearest listed city is Marquette, 247 km away.

Topography around Thunder Bay

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

Within 3 km, the terrain around Thunder Bay has only modest variations in elevation — a maximum elevation change of 20 m around an average of 188 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 297 m; within 80 km, significant variations in elevation — a maximum elevation change of 503 m.

The land around Thunder Bay is covered by artificial surfaces (41%) and trees (26%) within 3 km, trees (43%) and water (39%) within 16 km, and trees (57%) and water (40%) within 80 km.

3 km

20 m

artificial surfaces 41%

16 km

297 m

trees 43%

80 km

503 m

trees 57%

treesgrasslandcroplandartificial surfacesbare terrainwaterwetland

← March Thunder Bay year-round climate May →Best places to visit in April

April weather nearby: Marquette 247 km · Duluth 278 km · Superior 283 km · Hibbing 295 km · Wausau 382 km · Weston 389 km · Kenora 411 km · Marshfield 419 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

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 Thunder Bay (48.382°, -89.2502°, elevation 188 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).

	Avg high (°C)	Avg low (°C)
1	3	-6
2	3	-6
3	3	-5
4	4	-5
5	4	-5
6	4	-5
7	4	-5
8	4	-4
9	5	-4
10	5	-4
11	5	-4
12	5	-3
13	6	-3
14	6	-3
15	6	-3
16	6	-3
17	7	-2
18	7	-2
19	7	-2
20	7	-2
21	7	-2
22	8	-1
23	8	-1
24	8	-1
25	8	-1
26	8	-1
27	9	0
28	9	0
29	9	0
30	9	0

	Clearer (%)	Cloudier (%)
1	34	66
2	34	66
3	34	66
4	34	66
5	34	66
6	35	65
7	35	65
8	35	65
9	35	65
10	36	64
11	36	64
12	38	62
13	38	62
14	39	61
15	39	61
16	39	61
17	39	61
18	41	59
19	41	59
20	40	60
21	41	59
22	41	59
23	41	59
24	41	59
25	41	59
26	41	59
27	41	59
28	41	59
29	41	59
30	40	60

	Rain chance (%)	Snow chance (%)
1	28	21
2	28	21
3	28	21
4	28	21
5	28	21
6	28	21
7	28	21
8	28	20
9	27	20
10	27	19
11	27	19
12	27	18
13	27	18
14	27	17
15	27	17
16	27	16
17	27	16
18	27	15
19	27	15
20	27	15
21	27	14
22	27	14
23	28	13
24	28	12
25	28	12
26	28	11
27	28	11
28	28	10
29	29	9
30	29	9

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100

	Avg high (°C)	Avg low (°C)
1	3	-6
2	3	-6
3	3	-5
4	4	-5
5	4	-5
6	4	-5
7	4	-5
8	4	-4
9	5	-4
10	5	-4
11	5	-4
12	5	-3
13	6	-3
14	6	-3
15	6	-3
16	6	-3
17	7	-2
18	7	-2
19	7	-2
20	7	-2
21	7	-2
22	8	-1
23	8	-1
24	8	-1
25	8	-1
26	8	-1
27	9	0
28	9	0
29	9	0
30	9	0

	Clearer (%)	Cloudier (%)
1	34	66
2	34	66
3	34	66
4	34	66
5	34	66
6	35	65
7	35	65
8	35	65
9	35	65
10	36	64
11	36	64
12	38	62
13	38	62
14	39	61
15	39	61
16	39	61
17	39	61
18	41	59
19	41	59
20	40	60
21	41	59
22	41	59
23	41	59
24	41	59
25	41	59
26	41	59
27	41	59
28	41	59
29	41	59
30	40	60

	Rain chance (%)	Snow chance (%)
1	28	21
2	28	21
3	28	21
4	28	21
5	28	21
6	28	21
7	28	21
8	28	20
9	27	20
10	27	19
11	27	19
12	27	18
13	27	18
14	27	17
15	27	17
16	27	16
17	27	16
18	27	15
19	27	15
20	27	15
21	27	14
22	27	14
23	28	13
24	28	12
25	28	12
26	28	11
27	28	11
28	28	10
29	29	9
30	29	9

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100

	Avg high (°C)	Avg low (°C)
1	3	-6
2	3	-6
3	3	-5
4	4	-5
5	4	-5
6	4	-5
7	4	-5
8	4	-4
9	5	-4
10	5	-4
11	5	-4
12	5	-3
13	6	-3
14	6	-3
15	6	-3
16	6	-3
17	7	-2
18	7	-2
19	7	-2
20	7	-2
21	7	-2
22	8	-1
23	8	-1
24	8	-1
25	8	-1
26	8	-1
27	9	0
28	9	0
29	9	0
30	9	0

	Clearer (%)	Cloudier (%)
1	34	66
2	34	66
3	34	66
4	34	66
5	34	66
6	35	65
7	35	65
8	35	65
9	35	65
10	36	64
11	36	64
12	38	62
13	38	62
14	39	61
15	39	61
16	39	61
17	39	61
18	41	59
19	41	59
20	40	60
21	41	59
22	41	59
23	41	59
24	41	59
25	41	59
26	41	59
27	41	59
28	41	59
29	41	59
30	40	60

	Rain chance (%)	Snow chance (%)
1	28	21
2	28	21
3	28	21
4	28	21
5	28	21
6	28	21
7	28	21
8	28	20
9	27	20
10	27	19
11	27	19
12	27	18
13	27	18
14	27	17
15	27	17
16	27	16
17	27	16
18	27	15
19	27	15
20	27	15
21	27	14
22	27	14
23	28	13
24	28	12
25	28	12
26	28	11
27	28	11
28	28	10
29	29	9
30	29	9

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100