Haarlem's weather is characterized by mild temperatures throughout the year, with a relatively narrow range between seasons. Winters are cool and slightly variable, with January averaging around 6°C and December around 8°C. Springs are also quite moderate, with March and April temperatures hovering around 6°C. Summer months bring warmer temperatures, with June and July averaging around 15-17°C, but the overall temperature range remains relatively contained. Autumns are similarly mild, with September and October temperatures ranging from 11-18°C on average.