My first-ever foal was born in July of last year. And my friend bought a mare from the same place, and her foal was born in August. We have pretty cold winters and they did fine.
They did have access to a run-in shed, and plenty of hay. But we didn't have to blanket or anything, and we get snow. And believe me, I am a worrier! If there is something to worry about, I will find it.
Yes, get a good book or two to read in the meantime. Blessed are the Broodmares is good, but to me it read more like a novel than something you could turn to in an emergency. I found specific information was hard to locate sometimes. I really like this one, because even though (thank goodness) I didn't have an emergency, I felt this one gave you good info in case you had one:
If I could only have bought one book in preparation for a foal, that would be the one I thought was the best.
This one below is a nice little book too, as it talked about what to do in the months after your foal is born. It's not as detailed as Blessed are the Broodmares or The Complete Book of Foaling. But it has a lot of nice pictures and is a good beginner's book that I enjoyed reading.