Last Blast of Heat Today Before Sioux Lookout Shifts Toward Showers, Thunderstorms, and a Cold Snap by Weekend

SIOUX LOOKOUT – WEATHER REPORT – Sioux Lookout is basking in one more day of summer-like heat, as the Heat Warning from Environment Canada remains in effect for the final stretch today. Temperatures are forecast to hit 29°C this afternoon, with a humidex of 31 making it feel extra tropical. But enjoy (or endure) it while you can—because a dramatic change is waiting in the wings. Starting tonight, showers and thunderstorms will begin cooling the region down, with temperatures expected to nosedive by the weekend, bringing the risk of flurries on Saturday night. Yes, in May.

From Sizzling Sunshine to Stormy Skies and a Weekend Freeze

At 4:00 AM CDT, Sioux Lookout Airport reported clear skies and a warm 17.1°C. Humidity is at 57%, with a dew point of 8.4°C, and a gentle south-southeast wind blowing at 12 km/h. The pressure is at 100.4 kPa and rising, offering a brief moment of stability before the weather tumbles.

Today’s forecast is classic late-spring Prairie heat—sunny this morning and early this afternoon, followed by a mix of sun and cloud. Showers will move in with a 40 percent chance of precipitation and a risk of thunderstorms developing this afternoon. The high will reach a toasty 29°C, with a humidex of 31, and the UV index will climb to 7—high—meaning sun protection is still essential despite the clouds building later.

Tonight will be partly cloudy with a lingering 40 percent chance of showers and the risk of thunderstorms early in the evening. Winds will shift to the east at 20 km/h before becoming light later tonight. The low will dip to 14°C—still warm but marking the beginning of the cool-down.

Thursday will bring more clouds with a 40 percent chance of showers and the risk of an afternoon thunderstorm again. Winds will swing southeast at 20 km/h by afternoon, with a cooler high of 22°C, and a humidex of 26. The UV index will drop to 3—moderate—as thicker clouds take over.

Thursday night remains cloudy with a 40 percent chance of showers and a low of 12°C.

Friday will see heavier showers, with a 60 percent chance of rain and a much cooler high of just 17°C. The night will remain cloudy with a 40 percent chance of showers and a low of 7°C.

Saturday will be the shocker—cloudy with a 40 percent chance of showers and a high of only 6°C. Overnight, expect cloudy periods with a 40 percent chance of rain showers or flurries, as temperatures tumble to -2°C. Yes, flurries. In May. Sioux Lookout’s classic spring unpredictability on full display.

Sunday will see a slight recovery, with a mix of sun and cloud and a 40 percent chance of showers or flurries, but a more springlike high of 12°C. Sunday night will clear up with a low of -1°C. Monday will finally bring back the sunshine with a high of 18°C.

Staying Safe as the Heat Ends Abruptly

Today is your last chance to practice heat safety—stay hydrated, wear light clothing, and seek shade during peak afternoon heat. But also keep an eye on the sky for rapidly developing thunderstorms. With the wild temperature swings, those sensitive to weather shifts should brace for a bumpy ride through the weekend.

Sioux Lookout Weather Trivia

Did you know? Sioux Lookout is no stranger to late-season snowflakes. In fact, the region has recorded measurable snow as late as mid-June, making this weekend’s chance of flurries, while shocking, not entirely unprecedented.

Sioux Lookout’s May 14 Records

The record high for this day is 31.2°C, while the record low is -4.1°C. Today’s high of 29°C will make a strong showing, but by Saturday night’s plunge to -2°C, we’ll once again see Sioux Lookout flexing its title as one of Ontario’s springtime weather wildcards.