Amsterdam is only 7 feet above sea level, so the city is always a little damp. There is high humidity in the summer and a fair amount of rain, especially in the winter. The temperatures are rarely extreme, though, and there are many balmy days, especially in June, July, and August. November to April is overcast and windy with a bit of snow and ice around the New Year. Whatever the weather, it doesn't hang about for long, so wear layers and bring a good umbrella.
There are two main seasons in Amsterdam. Tulip time runs mid-March–mid-May, when the global rush to the bulb fields is matched by a surge in hotel bookings and a lengthy line for the Anne Frank House. The city also bustles April–September, when there is an enormous variety of cultural events and festivals: both King’s Day (April 27) and Museum Night (during the first week in November) are worth visits in their own right. Take advantage of Open Garden Days (third weekend in June) and Open Monument Day (second weekend in September) to see heritage properties and some extraordinary gardens that are otherwise rarely open to the public. The Hartjesdagen or "Hearts Days" festival, with a fun cross-dressing aspect, takes place during the third weekend in August.