Grande Prairie has a northern continental climate typical of northwestern Alberta and northeastern British Columbia, classified as humid continental are rare, occurring on average only two to three days a year, which is not unexpected this far north. Winter conditions can vary tremendously from year to year. Winters have been known to be mild enough to produce “brown Christmas” conditions, where little or no snow may fall until after Christmas due to unusually mild early winter conditions.
The average January temperature is −13.6 °C (7.5 °F), while the average July temperature is 16.2 °C (61.2 °F). However, temperatures as low as −52.2 °C (−62 °F) and as high as 35.6 °C (96 °F) have been recorded; the extreme humidex and wind chill readings are 40.8 and −63.0 °C (105 and −81 °F), respectively. The city receives 445 mm (17.5 in) of precipitation annually, including 322 mm (12.7 in) of rain and 154 cm (61 in) of snow. Snowfall amounts, however, vary greatly from year to year. Being fairly close to the foothills of the Canadian Rockies, it can get quite windy in Grande Prairie, especially in the spring and fall. Chinooks may occur in and bring winter thaws to the Grande Prairie area.
Grande Prairie has 314 days with measureable sunshine per year on average, and just above 2,200 hours of bright sunshine or about 46.1% of possible sunshine, ranging from a low of 31.2% in November to a high of 59.1% in July.
Summers can bring thunderstorms, although they are not as frequent nor as severe as those further south in Central Alberta. Rainfall can vary from year to year, but the Peace Region is noted for never having experienced truly severe drought conditions more typical of Southern Alberta and neighbouring Saskatchewan. Tornadoes are rare but not unheard of in the Peace Region. A tornado struck the downtown area and east side of Grande Prairie on July 8, 2004. Although the tornado was considered a very weak one (F0-F1 on the Fujita scale) and the weather was not severe at the time, it was still strong enough to damage houses and flip vehicles. There were no casualties or deaths.