Should I wear a winter type jacket in mid May?

Yes it gets colder at the top

I haven't been up there in May. But I would say yes just in case. Better be safe than sorry.

Definitely yes!

Yes! Yes! Yes!

Yes bring a heavy jacket gloves hat

It's cold take a jacket

Thanks for the advice.

Yes. It can bewarm at the base and cold, windy and wintery at the top.

Yes the weather changes very rapidly on Mt Washington

It's going to 48 with 35 mile an hour winds.