The Hague has a mild, maritime climate, very similar to England. Summers are generally warm with changeable periods, but excessively hot weather is rare. Rainfall is prevalent all year.
The best time to visit The Hague is during the summer months, especially if you plan on going to the beach resorts. Early or late summer is best - try to avoid the August crowds. Temperatures usually stay around 20°C with July and August being the warmest. Rainfall is consistent all year so make sure you have some waterproof clothing. Spring time is also a good time to visit when the flowers are in bloom (the tulips come out in May).
The Hague's weather is cooler during the winter months, although there isn't a huge change in weather between the seasons due to the maritime climate. The coldest temperatures occur in January and February, although the prevailing south-westerly winds are mild and usually bring a fair amount of rain. Clouds generally appear every day, and in the winter months fog often engulfs the area. Colder weather can see temperatures dip below freezing although snowfall is rare. Dress appropriately if you plan to visit during the winter.