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Another heat wave coming to Western New York and Southern Ontario

Buffalo Toronto Public Media | By Grant Ashley

Published August 10, 2025 at 11:16 AM EDT

Dozens of people lounge on the beach at Beaver Island State Park on Grand Island. Many of them have umbrellas and towels. The sky is blue, with some wispy clouds in the sky. — Swimming at a beach like this one at Beaver Island State Park on Grand Island is one way to stay cool.

Another multi-day heat wave is arriving in Western New York and Southern Ontario, just two weeks after a similar heat wave hit the region in late July.

The heat wave is forecasted to begin on Sunday and last through Wednesday, according to state officials, with the hottest temperatures coming on Monday and Tuesday. All of New York State and much of Ontario will be affected.

Heat index values — which measure how hot the weather feels to the average person — will reach the mid to upper 90s F in Western New York, according to state officials. Only one of Western New York's eight counties, Orleans County, is forecasted to see heat index values between 95 and 100 F. “Real feel” temperatures will be hottest in the afternoons and inland from the Great Lakes, according to the National Weather Service. Rain and higher humidity are expected in the region on Tuesday and Wednesday.

Canadian officials have issued a heat warning for Niagara Falls, Welland and the Southern Niagara Region with heat index values between 35 and 40 degrees Celsius, or 95-104 F. That warning is expected to last until Tuesday or possibly Wednesday.

Starting Sunday, heat & humidity with temps into the mid-90s are expected to impact the state through the week. Now is the time to prepare.

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When heat index values are between 90 and 103 F, the National Weather Service encourages exercising “extreme caution” due to an increased risk of heat exhaustion and heat stroke with prolonged exposure and/or physical activity. “Real feel” temperatures between 103 and 124 F are considered dangerous. Signs of heat stroke include high body temperature, red and dry skin with no sweat, a rapid pulse, dizziness and confusion.

This chart shows the caution classifications for various heat index values. Heat index values between 80 and 99 degrees Fahrenheit are in the "caution" category, with "fatigue possible with prolonged exposure and/or physical activity." Heat index values between 90 and 102 degrees Fahrenheit are in the "extreme caution" category, with "heat stroke, heat cramps, or heat exhaustion possible with prolonged exposure and/or physical activity." Heat index values between 103 and 124 degrees Fahrenheit are in the "danger" category, with "heat cramps or heat exhaustion likely, and heat stroke possible with prolonged exposure and/or physical activity." Heat index values between 103 and 124 degrees Fahrenheit are in the "danger" category, with "heat cramps or heat exhaustion likely, and heat stroke possible with prolonged exposure and/or physical activity." Heat index values at 125 or higher are in the "extreme danger" category, with "heat stroke highly likely."

“As extreme temperatures once again sweep across our state, I’m closely monitoring our forecasts and working alongside partners in government to ensure New Yorkers are protected,” Gov. Kathy Hochul said in a statement Sunday. “Extreme heat is the most dangerous weather event we face, and I ask all New Yorkers to please take proper precautions to keep themselves and their loved ones safe.”

New Yorkers and Ontarians can stay safe by staying in an air conditioned space, drinking water, staying out of the sun and taking frequent breaks if exercising or working outdoors.

The State Department of Health maintains a list of cooling centers, pools and splash pads in all eight of Western New York’s counties. You can find that list here.