If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Nieuwendam: The hottest months are usually July and August, with an average temperature of 16°C, while the coldest months are January and February, with an average of 4°C. The rainiest months in Nieuwendam are October, September, November and December, with each month seeing an average of 220 mm of rainfall.