You may have wonderful weather, but we can't predict what this year will bring. I would expect to have some rain or even snow at least once during that time. Just bring a raincoat and sneakers for those days.

It is very likely you will have some form of water falling from the sky during that time of year - rain, freezing rain, snow, sleet - so make sure you plan accordingly and have warm and waterproof footwear. Define "somewhat decent weather". It will be cool and could have raw winds in any of these cities. You could have some nice warm and sunny days and if you are cold-tolerant certainly you can stroll the cities.

One of the largest snowfalls ever in Boston was 4/1 some years ago. But last year my tulips were fully leafed out by the end of March.

That is very early spring and you may get warmish weather - but it can also be quite cold - esp at night. Expect rain on some days. And do realize that it is too early for most flowers and trees are typically still in bud rather than in leaf. (So don't expect countryside to be pretty.)

you might get lucky with some mild, sunny weather and you can count on it being too early for black flies!

Wunderground.com has a trip planner that will give you historic temps for those dates from previous years. No guarantee but will give you an isea.