Weather in Thunder Bay in April

A hard month. April is a hard month in Thunder Bay, and worth planning around. Highs sit at 9 °C and the day is short; this is an indoors-with-excursions month, not an outdoors-all-day one.

April ranks 7 of 12 in Thunder Bay: past the worst of the year but short of August, which is the month to book if the dates are open.

Rain on 10 days, 1 of them heavy. Enough to need a plan B, not enough to need a plan around it. Layers, and a genuinely waterproof outer — at 9 °C the difference between a good day and a miserable one is entirely down to what you are wearing.

What the averages hide

Averages flatten a month, and this one hides a few things: 19 nights fall below freezing. Across the twenty years measured, the hottest April day reached 21.6 °C and the coldest night fell to -13.5 °C, and the wettest single day dropped 41 mm — roughly 75% of the month's rain in one day.

April is moderately variable: 14 mm in the driest year against 201 mm in the wettest, around an average of 55 mm. Roughly two Aprils in three land near that average, and the third does something else entirely.

Wind is light at 3.7 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 72%.

How April sits in the year

The month is on the way up: 8.4 °C warmer than March, and May adds another 6.8 °C. Late in the month feels noticeably different from the start of it, which is worth knowing if the trip is short.

Daylight in April

13.6 hours of daylight, gaining 1.7 hours across the month. That is between Thunder Bay's extremes of 16.1 and 8.4 hours, so days are long enough not to constrain the plan.

An inland climate

Thunder Bay has no sea to moderate it, and it shows: 42 °C separates the hottest afternoon of the year from the coldest night. That is a genuinely continental range, and it means summer and winter here are barely the same place.

How busy it gets

Quiet. Few other visitors, cheaper rooms, and a real chance some seasonal operators are shut.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

April in Thunder Bay versus nearby

If Thunder Bay is one option among several, the nearby comparison is worth making. Minneapolis is a better bet in April — 4.5 °C warmer, 1 day more rain. Milwaukee is a better bet in April — 3.9 °C warmer, 1 day more rain.

So: April is a compromise. August is 34 points better and is what Thunder Bay is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in Thunder Bay

See all twelve months in Thunder Bay, or where else to go in April.