I have used a rugged ridge parka from LLBean for the past 12 years and just bought a second updated version this year. It is perfect for the really cold windy days that happen in the deep of the winter months. Wind chill is going to be what you need protection from, and this parka does a good job keeping the wind at bay. Otherwise, vests are good at 50° or so, and a light down jacket will take you between 50° and 25°, chillier if you layer a shirt and sweater or hoodie beneath. Give yourself plenty of time to acclimate to the temp differences. Your body is used to warmer temps, so warmer temps to Mainers will be much different than warmer temps to you, believe me. Dress as you need to for your comfort.