Thunder Bay weather in August 2025

Expect 72°F daytime maximum temperatures in the shade with on average 8 hours of sunshine per day in Thunder Bay in August. Check more long-term weather averages for Thunder Bay in August before you book your next holiday to Ontario in 2025/2026.

  • 72°F maximum daytime temperature in August in Thunder Bay72
    72°F max day temperature
  • 8 hours of sunshine per day
  • 13 days with some rainfall in August in Thunder Bay13
    13 days with some rainfall
  • 50°F minimum night-time temperature in August in Thunder Bay50
    50°F min night temperature
  • 14 hours of daylight per day in August in Thunder Bay14
    14 hours of daylight per day
  • No heat & humidity in August in Thunder Bay0
    No heat & humidity
  • 3.5 inches monthly rainfall in August in Thunder Bay3.5
    3.5 inches of monthly rainfall
  • UV (maximum) index 6 (High) in August in Thunder Bay6
    6 (High) UV index
  • 55°F sea temperature in August in Thunder Bay55
    55°F sea temperature

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The August weather guide for Ontario (Thunder Bay) shows long term weather averages processed from data supplied by CRU (University of East Anglia), the Met Office & the Netherlands Meteorological Institute. Find out more about our data sources.

Metric (°C)  |  Imperial (°F)

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How hot is it in Thunder Bay in August?

Daytime temperatures usually reach 72°F in Thunder Bay in August, falling to 50°F at night.

How sunny is it in Thunder Bay in August?

There are normally 8 hours of bright sunshine each day in Thunder Bay in August - that's 58% of daylight hours.

How warm is the sea around Thunder Bay in August?

The average sea temperature around Thunder Bay in August is 55°F.

Does it rain in Thunder Bay in August?

There are usually 13 days with some rain in Thunder Bay in August and the average monthly rainfall is 3.5 inches.

Thunder Bay August sunrise & sunset times

Browse the sunrise and sunset times for Thunder Bay in August 2025. Select a month to view Thunder Bay sunrise and sunset times for the next 12 months.

JanFebMarAprMayJunJulAugSepOctNovDec

Date Sunrise times Sunset times
Friday, 1st August 2025 05:32 20:34
Saturday, 16th August 2025 05:53 20:09
Sunday, 31st August 2025 06:13 19:40

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