You might spend a lot of your vacation inside, but if you're planning to venture beyond the casino, looking at local weather trends is a good idea. The hottest months are usually July and August with an average temp of 61°F, while the coldest months are January and February with an average of 38°F. The rainiest months in Nieuwendam are October, September, November, and December, with each month seeing an average of 9 inches of rainfall.