Should your vacation in Europe fall in
autumn, we recommend you try and push it to the first half of the season (September to mid-October). This will allow you to get the best out of your trip.
During this period, both the Netherlands and Belgium are comfortably warm, but there are much fewer tourists, which is a huge advantage if you want to immerse yourself into the local culture and be able to breathe while visiting the landmarks. (Well, on our
private and small group tours to the Netherlands and Belgium, we make sure you have your skip-the-line entrance tickets anyway, so don't you worry, we'll take care of you in any season.)
My personal experience of traveling to the Netherlands in the end of September was great, and unless you aim to see the legendary tulip fields, I would say early fall is the best time to visit Benelux countries.