Thunder Bay Weekend Weather: Warm Conditions Set Up Strong Finish for the 2026 CLETHUNDER BAY — Thunder Bay is heading into a warm, generally favourable summer weekend, good news for families planning to spend Saturday and Sunday at the Canadian Lakehead Exhibition. Saturday: Warm, Breezy and Increasingly CloudyThunder Bay started Saturday morning mainly sunny, with a temperature of 15 C at Thunder Bay Airport as of 8 a.m. The CLE fireworks show is scheduled for 11 p.m. Sunday. With Environment Canada forecasting a clear Sunday night, the weather outlook as of Saturday morning is encouraging for the fireworks. The Weekend at a GlanceSaturday, Aug. 8: Increasing cloudiness, high 24 C, humidex 26.