Winters in Cormeilles-en-Parisis are cold and unpredictable, with temperatures often dropping below freezing in January and February. Spring arrives slowly, with March and April bringing mild days but still chilly nights. Summer is warm and pleasant, with June and July experiencing the highest temperatures of the year, although they rarely exceed 30°C. Autumn brings a return to cooler weather, with September and October experiencing crisp mornings and afternoons that can be quite cool. The temperature fluctuations throughout the seasons are notable, with significant variations between day and night.