Yes they can be started inside. And since you are zone 4 I would recommend it.

In long season climates, it would be better to start them in their final growing place so as to not confine and later disturb their roots. But since they require warm soil to sprout and like 120 days to mature, starting them indoors is often a good idea for us non-tropical folks.

I usually start some of mine 3 weeks before planting outside. I would not recommend you start them inside any earlier than 4 weeks before transplanting. You shouldn't have a problem transplanting them outside, as long as you are careful not to disturb the roots too much.

Thanks,
I will start them when I start my melons.
Thanks again, Lola

Should us zone 6-ers start them inside as well? I'm assuming I should start butternut and acorn squash seeds inside around the 2nd week of April. Has anyone done this?

I start mine inside, no more than 3 weeks before they go into the ground, but i'm sure 4 weeks or so wouldn't hurt them, especially since your season is so much shorter than here. They seem to do better if you take a few extra days of hardening off.
good luck!

I'm sure that you could start them indoors in zone 6 or zone 5 but I've grown butternut squash for 3 seasons now and I've never had problems with them ripening before the frost after direct sowing them and I'm here in zone 5. Just wanted to share that info!

Whatever you do, do grow them! Butternut squash are fantastic keepers and taste wonderful. I usually get 10-12 good sized squashes off of 3 plants.

I'm zone 5 (s. wisc) and I have better luck direct seeding my melons, squash, pumpkins than I do starting them early.

My dad is zone 4 ( middle wisc) and he needs to get a head start on those plants in order to guarantee production.

Hard to believe what a difference 150 miles can make.