April is close to Thunder Bay's year-round average, with average highs near 7.8°C and lows around -2.6°C (mean 2.6°C). It is about average for rainfall, averaging 52 mm of rainfall and 73% relative humidity across the period.
April is close to Thunder Bay's year-round average. Across 45 years of records, the warmest April in Thunder Bay was 1987 — when the month averaged 6.7°C — while the coldest was 1996 at -0.7°C. Typical April days reach 7.8°C with nights near -2.6°C. The long-term trend is cooling, about 0.2°C per decade.
April is about average for rainfall in Thunder Bay, averaging 52 mm of rainfall. The wettest April on record was 2001 with 201 mm, while the driest was 1987 at 5 mm.
Relative humidity in Thunder Bay during April averages 73%. The most humid April was 2001 at 84%, and the least humid was 1998 at 63%.
April receives about 4.6 kWh/m²/day of solar energy in Thunder Bay. The sunniest April was 1998 at 5.4 kWh/m²/day, and the cloudiest was 2022 at 3.6.
Average wind speed in Thunder Bay during April is 1 m/s. The windiest April was 2023 at 1.3 m/s, while the calmest were 1991, 1993 and 2005, among others at 0.9 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 3.0°C | 2.6°C | 3.1°C | 2.2°C | 1.9°C | -1.1°C |
| Avg High | 8.3°C | 7.9°C | 8.3°C | 7.5°C | 6.6°C | -1.7°C |
| Avg Low | -2.3°C | -2.8°C | -2.1°C | -3.0°C | -2.7°C | -0.4°C |
| Avg Rain | 42 mm | 42 mm | 68 mm | 45 mm | 73 mm | +31 mm |
April temperatures in Thunder Bay have stayed relatively stable across the record.
April has ranged from a record low of -23°C (1982) to a record high of 24.7°C (1998).
Rainfall in April is about average for rainfall, averaging 52 mm, with a wettest year of 201 mm.
A good time to visit Thunder Bay
April is a good time to visit Thunder Bay, with days averaging 7.8°C and nights around -2.6°C (mean 2.6°C, close to Thunder Bay's yearly average) and moderate rainfall. August and July are marginally more temperate, but April still suits most travellers.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 7.2°C | 2.1°C | -3.0°C | 15.9°C | -11.3°C | 83 mm | 76% | 1 m/s | 4 |
| 2024 | 8.4°C | 3.3°C | -1.8°C | 15.0°C | -8.4°C | 66 mm | 74% | 1.1 m/s | 4.5 |
| 2023 | 5.0°C | 0.6°C | -3.8°C | 23.9°C | -12.2°C | 88 mm | 81% | 1.3 m/s | 3.9 |
| 2022 | 3.8°C | 0.1°C | -3.6°C | 10.0°C | -10.4°C | 103 mm | 79% | 1.2 m/s | 3.6 |
| 2021 | 9.0°C | 3.9°C | -1.1°C | 15.9°C | -9.8°C | 73 mm | 73% | 1 m/s | 4.4 |
| 2020 | 6.3°C | 1.6°C | -3.0°C | 16.9°C | -7.9°C | 23 mm | 70% | 1 m/s | 4.9 |
| 2019 | 7.6°C | 2.8°C | -2.1°C | 17.9°C | -9.4°C | 44 mm | 73% | 1 m/s | 4.2 |
| 2018 | 5.3°C | -0.3°C | -5.9°C | 18.8°C | -14.2°C | 14 mm | 65% | 1.1 m/s | 5 |
| 2017 | 8.8°C | 3.5°C | -1.7°C | 19.4°C | -6.7°C | 65 mm | 75% | 1 m/s | 4.5 |
| 2016 | 6.4°C | 1.0°C | -4.3°C | 18.4°C | -14.0°C | 28 mm | 73% | 1 m/s | 4.9 |
| 2015 | 8.2°C | 2.8°C | -2.6°C | 17.5°C | -11.6°C | 49 mm | 69% | 1 m/s | 5 |
| 2014 | 5.2°C | 0.3°C | -4.6°C | 15.1°C | -14.6°C | 56 mm | 78% | 1.1 m/s | 4.2 |
| 2013 | 4.5°C | 0.1°C | -4.3°C | 17.9°C | -12.0°C | 55 mm | 76% | 1.2 m/s | 3.9 |
| 2012 | 9.2°C | 3.4°C | -2.4°C | 13.4°C | -8.9°C | 45 mm | 69% | 1 m/s | 5.2 |
| 2011 | 7.6°C | 2.6°C | -2.4°C | 17.6°C | -9.6°C | 58 mm | 74% | 1.1 m/s | 4.3 |
| 2010 | 12.1°C | 6.2°C | 0.3°C | 20.3°C | -3.9°C | 34 mm | 67% | 1 m/s | 5.3 |
| 2009 | 7.8°C | 3.0°C | -1.8°C | 18.4°C | -6.6°C | 71 mm | 75% | 1 m/s | 4.5 |
| 2008 | 7.5°C | 2.8°C | -1.8°C | 17.3°C | -6.0°C | 65 mm | 75% | 1.1 m/s | 4.1 |
| 2007 | 8.7°C | 3.0°C | -2.6°C | 20.0°C | -13.6°C | 53 mm | 69% | 1.1 m/s | 5.1 |
| 2006 | 12.1°C | 6.1°C | 0.1°C | 18.3°C | -5.2°C | 34 mm | 71% | 1 m/s | 5.1 |
| 2005 | 10.9°C | 5.0°C | -0.8°C | 20.5°C | -4.3°C | 21 mm | 71% | 0.9 m/s | 5 |
| 2004 | 7.9°C | 2.8°C | -2.3°C | 15.0°C | -5.5°C | 52 mm | 72% | 1 m/s | 4.8 |
| 2003 | 7.2°C | 1.7°C | -3.8°C | 18.7°C | -13.1°C | 82 mm | 70% | 1.1 m/s | 4.9 |
| 2002 | 6.4°C | 1.9°C | -2.6°C | 14.8°C | -9.0°C | 47 mm | 76% | 1 m/s | 4.5 |
| 2001 🌧️ | 7.6°C | 2.9°C | -1.7°C | 19.3°C | -8.0°C | 201 mm | 84% | 1 m/s | 3.8 |
| 2000 | 7.2°C | 1.8°C | -3.6°C | 19.7°C | -10.3°C | 50 mm | 71% | 1.1 m/s | 4.7 |
| 1999 | 10.3°C | 4.9°C | -0.5°C | 23.4°C | -4.3°C | 41 mm | 72% | 1 m/s | 5.2 |
| 1998 | 12.0°C | 5.7°C | -0.5°C | 24.7°C | -4.3°C | 17 mm | 63% | 1 m/s | 5.4 |
| 1997 | 7.6°C | 2.1°C | -3.5°C | 14.5°C | -12.4°C | 25 mm | 72% | 1 m/s | 5.1 |
| 1996 ❄️ | 4.3°C | -0.7°C | -5.7°C | 12.4°C | -14.5°C | 39 mm | 77% | 1 m/s | 4.9 |
| 1995 | 5.5°C | 0.5°C | -4.6°C | 10.5°C | -16.7°C | 23 mm | 69% | 1.1 m/s | 4.4 |
| 1994 | 7.5°C | 2.0°C | -3.5°C | 20.2°C | -12.4°C | 60 mm | 69% | 1.2 m/s | 4.7 |
| 1993 | 7.1°C | 2.1°C | -2.8°C | 15.0°C | -9.5°C | 49 mm | 65% | 0.9 m/s | 4.2 |
| 1992 | 6.2°C | 1.3°C | -3.5°C | 12.7°C | -10.8°C | 41 mm | 75% | 1 m/s | 4.7 |
| 1991 | 10.6°C | 5.0°C | -0.7°C | 21.0°C | -9.1°C | 63 mm | 71% | 0.9 m/s | 4.8 |
| 1990 | 8.0°C | 2.8°C | -2.4°C | 22.2°C | -13.1°C | 64 mm | 73% | 1.1 m/s | 4.5 |
| 1989 | 6.6°C | 1.5°C | -3.6°C | 15.7°C | -14.1°C | 29 mm | 73% | 0.9 m/s | 4.9 |
| 1988 | 8.9°C | 3.5°C | -2.0°C | 18.9°C | -8.2°C | 12 mm | 64% | 1 m/s | 5.2 |
| 1987 🔥 | 13.4°C | 6.7°C | 0.0°C | 20.5°C | -9.6°C | 5 mm | 68% | 0.9 m/s | 5.1 |
| 1986 | 9.9°C | 4.7°C | -0.5°C | 18.8°C | -6.7°C | 63 mm | 75% | 1.1 m/s | 4.1 |
| 1985 | 8.5°C | 3.5°C | -1.5°C | 20.7°C | -11.9°C | 47 mm | 77% | 1.1 m/s | 4.6 |
| 1984 | 8.9°C | 4.1°C | -0.7°C | 17.3°C | -6.4°C | 37 mm | 74% | 1.1 m/s | 4.8 |
| 1983 | 6.0°C | 1.2°C | -3.5°C | 19.7°C | -14.8°C | 59 mm | 82% | 1.1 m/s | — |
| 1982 | 4.7°C | -0.6°C | -6.0°C | 20.7°C | -23.0°C | 59 mm | 81% | 1.2 m/s | — |
| 1981 | 7.9°C | 2.7°C | -2.6°C | 16.7°C | -9.5°C | 65 mm | 75% | 1.1 m/s | — |
Actual recorded April data for each year, 1981–2025 — sourced from NASA POWER.
The average high in April is around 7.8°C with lows near -2.6°C (mean 2.6°C), based on 45 years of NASA POWER data.
April averages 52 mm of rainfall in Thunder Bay, about average for rainfall. The wettest on record was 201 mm in 2001.
The hottest April reached 24.7°C in 1998. The coldest dipped to -23°C in 1982.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average April temperatures have fallen by about 0.2°C — but days and nights have moved in opposite directions. Overnight lows rose from -2.9°C to -2.7°C while daytime highs eased from 7.2°C to 6.7°C, narrowing the gap between day and night.
April is close to Thunder Bay's year-round average and about average for rainfall, so plan for around 7.8°C daytime highs and -2.6°C at night.
Not quite — April is the 6th coolest month in Thunder Bay, averaging 2.6°C.
For April in Thunder Bay, pack warm layers and a jacket for chilly mornings, with typical highs of 7.8°C and lows of -2.6°C. Bring an umbrella or light rain jacket too.
Relative humidity in April averages 73% — moderately humid.
Average wind speed in April is 1 m/s. The windiest April on record averaged 1.3 m/s (2023).
The wettest April on record was 2001 with 201 mm. On average, April sees 52 mm.
All figures are derived from NASA POWER (Prediction Of Worldwide Energy Resources), based on MERRA-2 satellite reanalysis, covering 1981–2025.
Explore how the weather in Thunder Bay behaves each April, based on 45 years of NASA POWER climate data from 1981 to 2025. This page breaks down average temperatures, rainfall, humidity, wind and solar radiation for April specifically, along with year-by-year records and how the month has changed over the decades.
