In Massachusetts the practical exterior painting season runs from late spring into early fall. The limit isn't the daytime high; it's the overnight low and the moisture that comes with it. Most exterior paints list a minimum application temperature, and the surface needs to stay above it while the paint cures, not just while it's going on.
Dew is the less obvious problem. On cool nights in September and October, siding gets wet by late afternoon. Paint applied too late in the day can stay soft, collect dew, and dry with a streaky or uneven finish. That's why fall jobs often run on shorter days, starting once the morning dew burns off and stopping early enough for the paint to set before evening.
Spring has its own issues. Siding that looks dry can still hold moisture after a wet week, especially on shaded walls. Painting over damp wood is one of the most common causes of peeling and blistering a year or two later.
If your house needs a repaint, the best move is to get an estimate early. That gives you time to pick colors, sort out any carpentry repairs, and get on the schedule for the weeks with the most reliable weather.