From Below Freezing to Bright and Breezy — Classic May in Thunder Bay

A Crisp Morning Begins a Gradual Warm-Up

Thunder Bay is waking up with a sharp bite in the air this Sunday, with the temperature sitting at -1.3°C as of 7:00 AM at the Thunder Bay Airport. With a matching dew point, we’ve got 100% humidity — so if you feel like you’re walking through a fridge, you’re not alone. A barely-there north wind at 2 km/h gives us a modest wind chill of -2°C. The good news? Visibility is excellent at 32 kilometres, and better still — sunshine is on the way.

The barometric pressure is at a healthy 101.9 kPa and rising, suggesting stable and improving weather throughout the day. While fog patches will dissipate through the morning, expect the sun to take over the skies. Winds will swing to the east and increase to 20 km/h late this morning, and the high will rise to 11°C. The UV index reaches a 7, meaning it’s a strong sun day — you’ll want sunscreen even if it feels like late winter first thing.

Tonight: Clear and Crisp

The skies will stay clear into the night, and temperatures will bottom out around zero. It’s the kind of spring night where your furnace and your patio lights might both see some action.

Monday: Sunny and Milder

Monday continues the upward trend, with sunny skies and a high of 15°C — a welcome shift into more comfortable territory. With a UV index still at 7, make sure your sun protection habits are in mid-season form. The evening will stay clear with a low of +4°C, ideal for a walk or simply opening the windows for some cool, fresh air.

Tuesday and Wednesday: Warm to Cold (Again)

Tuesday brings a mix of sun and cloud along with a 30 percent chance of showers, but also the warmest day in the outlook with a high of 19°C. That warmth won’t stick around long, though. The night cools off to 2°C, and Wednesday brings a more subdued high of 11°C under partly sunny skies.

Wednesday night dips sharply again to -3°C — just in case you were thinking about putting those frost covers away. Thunder Bay says: not so fast.

What to Wear

Start your Sunday bundled in a warm coat and gloves, but bring layers — by midday the sunshine will warrant something lighter. Monday and Tuesday are great for spring jackets, sunglasses, and SPF, but don’t pack away the mittens just yet. Wednesday night’s frost will have the final say.

Thunder Bay Trivia: A City of Spring Contrasts

On May 4th, Thunder Bay has experienced a range of weather extremes. The record high was a balmy 27.6°C back in 2001, while the record low — a chilling -7.8°C — was recorded in 1974. Today’s start at -1.3°C with a high of 11°C fits perfectly within the city’s proud tradition of seasonal indecisiveness.