Northerner,

I'm a southerner here in Georgia, but I can give you some guidelines that may help:
1. Minimim soil planting temp: 60 degrees.
2. Optimum growing temp: 65 to 75 degrees. (they don't like it cold at night, so row covers and/or black plastic mulch are probably helpful for your climate)
3. Transplant out after 3-4 weeks max following germination.
4. Grow transplants in 3-4 inch pots from the beginning to avoid root disturbance at all costs!
(don't use those peat pots, though, and expect to plant them directly in the ground, because they don't break down quickly enough and you'll wind up with root bound plants!)

So depending on when you started your squash seed, you may want to start over, so your transplants mature at the right time, but you haven't lost as much time as you thought, casue they don't grow indoors as long as tomatoes and peppers. Take heart, it can be done, so go for it!

Best of Luck!
Susan

Susan, thank you so much for your detailed information. All may not be lost though, because all these seeds germinated around April 30, and our big plant out weekend here is May 24 which should be within the range you mentioned for plant out after germination. However, I think I will re-start the Waltham squash. I planted them out in pots just two nights ago, and I was amazed at the size of the roots in just a couple of days. I am very excited about growing these veggies. Now I have to amend my soil and think about somewhere to grow them. I am thinking of having them sprawl on a 3 foot tall 6 foot long woodpile which is an eye-sore in my yard. The plants would cover it nicely. I will have to be on the lookout for slugs though. Thanks for your encouragement and Happy Gardening.
Northerner.