Green Bay experiences cold winters with temperatures often dropping below -20°C in January and February, but mild periods bring highs above 0°C. Spring is a slow warming period, with temperatures gradually rising from around 3°C in March to 12°C in May. Summer months see relatively stable high temperatures, averaging around 21-22°C from June to August. Autumn brings cooling temperatures, with September's average high of 17°C and October's brief warmth before dropping back down. By December, temperatures are once again below -20°C.