Winters in Saint-Martin-d'Heres are cold and variable, with temperatures often dropping below freezing in January and December. Spring arrives slowly, with March temperatures still ranging from -3°C to 27°C, but by April and May, the average temperature has risen significantly, often reaching up to 13°C or more. Summers are mild and pleasant, with July and August being the warmest months, averaging around 20°C. As autumn sets in, temperatures drop rapidly, returning to chilly averages by November. The coldest periods are typically from January to February and December, while the warmest months are June, July, and August.