Glendale Heights experiences a moderate climate with distinct seasonal variations. Winters are cold, with temperatures often below freezing, and average highs around 0°C in January and February. As spring approaches, temperatures gradually rise, reaching averages of 10°C by April and 15°C by May, marking the beginning of warmer months. Summer is warm to hot, with July and August averaging highs above 24°C, while September brings a slight cooldown. Autumn sees temperatures drop again, with November and December experiencing average lows around 0°C, returning to winter's chill.