We have just updated our end of May weather forecast for Amsterdam. It's nothing to write home about: Quite cool and slightly changeable weather, with sunny intervals and a few showers.
The weather pros "promise" warmer temperatures will be back toward the middle of June. That said, to us Dutch folks this weather isn't all that bad. There are plenty of sunny intervals, and it's mild enough to go for a stroll and sit at a terrace with a pint or a glass of wine.
Don't want to stay outside? Amsterdam has some 40 museums — 85 if you look at the Greater Amsterdam region.
And that's not counting tourist traps like like the "Cheese Museum," the "Tulip Museum," or the "Erotic Museum." 
Photo: Tourist trap museums in Amsterdam.
You did not come all the way to Amsterdam to waste your time and money in a shop, right? But hey, if you're the type of tourist who likes such stores masquerading as museums, be sure to visit the milk and bread museum at a local supermarket.
As for real museums, be sure to get skip-the-line tickets ahead of time. Not only do you not want to spend your precious vacation time standing in line: since the pandemic many museums switched to time slot tickets only. The earlier you buy your ticket, the more choice of time slots you have.