Thunder Bay weather in December

In December, Thunder Bay sees average daytime highs of -6°C and overnight lows near -13°C, with 38 mm of precipitation across 7.3 wet days and about 8.2 hours of daylight. It is the 10th-warmest and 9th-wettest month of the year here.

Highs ease over the month, from about -3°C in the first days to -8°C by the end. The sky is clear or mostly clear about 18% of the time in December, and the air most often feels dry.

Daylight stretches from about 8 h 24 min at the start of December to 8 h 12 min by month's end. Set against the rest of the year, December is Thunder Bay's 11th-clearest and 3rd-windiest month. For the whole year in context, see Thunder Bay's year-round climate.

Daytime high
-6°
10th warmest
Overnight low
-13°
3rd coldest
Precipitation
38 mm
7.3 wet days
Daylight
8 h 06 min
8:49 AM – 4:57 PM
Cloud cover
73%
11th clearest
Wind
14 km/h
3rd windiest
Solar energy
1.12 kWh/m²
Travel score
0.0
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.

Temperature in December

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about -3°C in the first days to -8°C by the end.

A typical December day in Thunder Bay reaches about -6°C in the afternoon and slips back to -13°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between -15°C and 2°C. Set against its neighbours, December runs about 7°C cooler than November and about 4°C warmer than January.

-30°-20°-10°151015202531
Avg high (°C)Avg low (°C)
1-3-10
2-3-10
3-3-10
4-4-10
5-4-11
6-4-11
7-4-11
8-4-11
9-5-12
10-5-12
11-5-12
12-5-12
13-5-12
14-5-13
15-6-13
16-6-13
17-6-13
18-6-13
19-6-14
20-6-14
21-7-14
22-7-14
23-7-14
24-7-15
25-7-15
26-8-15
27-8-15
28-8-16
29-8-16
30-8-16
31-8-16

How December really feels in Thunder Bay

Once humidity and wind are folded in, December averages 0 days that feel above 32°C and 31 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
31
31 feel bitter (≤ -10°C)

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

Thunder Bay weather by month

How December compares with the rest of the year at a glance. December is the 10th-warmest and 9th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan-10° / -18°296.57.58.60.0
Feb-7° / -16°224.95.49.90.0
Mar-1° / -10°316.85.611.60.0
Apr / -3°548.3513.40.7
May13° / 6610.10.8153.5
Jun19° / 10°6510.5015.85.8
Jul22° / 14°7610.6015.56.6
Aug22° / 13°679.1014.16.7
Sep17° / 8410.5012.45.2
Oct / 7210.41.310.61.7
Nov / -5°497.85.790.0
Dec-6° / -13°387.37.88.20.0

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 18% of the time in December.

Beyond those clear spells, partly cloudy skies cover about 11% of December, with mostly cloudy or overcast conditions the remaining 71%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
12575
22575
32575
42674
52674
62575
72773
82773
92773
102773
112773
122773
132773
142773
152773
162971
172971
182971
192971
202971
213070
223070
233070
243070
253169
263169
273367
283367
293466
303466
313466

Chance of precipitation in December

Any precipitationSnow

Thunder Bay gets around 38 mm of rain and snow over 7.3 wet days in December. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable precipitation averages around 24% and peaks near 24% on the wettest days, and about 8 days bring snow.

0%10%20%30%40%151015202531
Rain chance (%)Snow chance (%)
12424
22424
32424
42323
52323
62323
72323
82324
92324
102324
112324
122425
132425
142425
152426
162426
172426
182426
192426
202426
212426
222426
232426
242426
252426
262426
272426
282425
292425
302325
312325

Humidity in December

DryComfortableHumidMuggyOppressiveMiserable

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

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

0%25%50%75%100%151015202531
Dry (%)
1100
2100
3100
4100
5100
6100
7100
8100
9100
10100
11100
12100
13100
14100
15100
16100
17100
18100
19100
20100
21100
22100
23100
24100
25100
26100
27100
28100
29100
30100
31100

Wind in December

Winds average 14 km/h in December.

Across December, 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
514light breeze
614light breeze
714light breeze
814light breeze
914light breeze
1014light breeze
1114light breeze
1214light breeze
1314light breeze
1414light breeze
1514light breeze
1614light breeze
1714light breeze
1814light breeze
1914light breeze
2014light breeze
2114light breeze
2214light breeze
2314light breeze
2414light breeze
2513light breeze
2613light breeze
2713light breeze
2813light breeze
2913light breeze
3013light breeze
3113light breeze

Sunrise & sunset in December

DaylightNight

Daylight runs from about 8 h 24 min at the start of December to 8 h 12 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 12 minutes over December. Sunrise moves from 8:35 AM to 8:55 AM, and sunset from 4:59 PM to 5:05 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
18.48:354:59
28.48:364:59
38.48:374:58
48.38:384:58
58.38:394:57
68.38:404:57
78.38:414:57
88.28:424:57
98.28:434:57
108.28:444:57
118.28:454:57
128.28:464:57
138.28:474:57
148.28:484:57
158.18:494:57
168.18:494:57
178.18:504:57
188.18:514:58
198.18:514:58
208.18:524:58
218.18:524:59
228.18:534:59
238.18:535:00
248.18:545:00
258.18:545:01
268.18:545:01
278.18:555:02
288.18:555:03
298.18:555:03
308.28:555:04
318.28:555:05

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 1.12 kWh/m² — the year's lowest.

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 — December's 1.12 kWh/m² sits near the bottom.

00.511.52151015202531
Solar energy (kWh/m²)Level
11.2Dim
21.1Dim
31.1Dim
41.1Dim
51.1Dim
61.1Dim
71.1Dim
81.1Dim
91.1Dim
101.1Dim
111.1Dim
121.1Dim
131.1Dim
141.1Dim
151.1Dim
161.1Dim
171.1Dim
181.1Dim
191.1Dim
201.1Dim
211.1Dim
221.1Dim
231.1Dim
241.1Dim
251.1Dim
261.1Dim
271.2Dim
281.2Dim
291.2Dim
301.2Dim
311.2Dim
Planning a trip in December

Is December a good time to visit Thunder Bay?

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

0.0
Sightseeing
8th-best month of the year
0.0
Beach & pool
7th-best month of the year

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

What to pack for Thunder Bay in December

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

In December, Thunder Bay sees daytime highs around -6°C and nights near -13°C. Pack a warm layer and a heavy coat. About 7 days see rain.

a warm layera heavy coat

Sea temperature near Thunder Bay in December

The nearest coast averages about 4°C in December — 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.

0°5°10°15°JanFebMarAprMayJunJulAugSepOctNovDecbracingcool
Sea temperature (°C)Comfort
Jan2Bracing
Feb1Bracing
Mar1Bracing
Apr2Bracing
May3Bracing
Jun4Bracing
Jul9Bracing
Aug15Cool
Sep14Bracing
Oct10Bracing
Nov6Bracing
Dec4Bracing

UV index in Thunder Bay in December

LowModerateHighVery highExtreme

Clear-sky midday UV in December peaks around 1. 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.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJun 17UV 8Dec 21UV 1
UV index (midday)Level
Jan1Low
Feb2Low
Mar3Moderate
Apr5Moderate
May6High
Jun8Very high
Jul6High
Aug6High
Sep5Moderate
Oct3Moderate
Nov1Low
Dec1Low
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.

WausauWestonKenoraMarshfield

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
16 km
297 m
80 km
503 m
treesgrasslandcroplandartificial surfacesbare terrainwaterwetland
December 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
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 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).