Waukegan's winters are bitterly cold, with temperatures often plummeting below -23°C in February and staying relatively chilly throughout the season. As spring arrives, temperatures gradually warm up, with April and May bringing mild days that can rise above 30°C. Summer is warm to hot, with July and August temperatures frequently reaching highs of around 34°C. Autumn brings a return to cooler weather, with October's temperatures often dipping below 3°C by the end of the month. The coldest months are December and January, while June is usually the warmest.