They are the same instinct pointed at opposite ends of the calendar. Cuffing season pairs people up for winter warmth and company; freckling is its summer mirror — lighter, looser, and far more likely to repeat with the same person year after year.
Side by side
Aspect
Freckling
Cuffing season
Season
Summer
Autumn to winter
Driven by
Long light, loose plans
Cold, holidays, company
With
Someone already known
Often someone new
Ends
By fading
Around spring
What each one means
Freckling
Plainly, freckling is freckles coming out on skin. In dating slang it names something else: drifting into a romance each summer with someone already in your orbit, then letting it fade when the weather turns — and often repeating the whole cycle the following year.
Cuffing season is the cold-weather stretch — roughly Thanksgiving to Valentine's Day — when single people feel the pull to pair off into a short-term relationship to get through the winter, then often drift apart when it warms up.