Summer is not my favourite season, and what could possibly be a nn ... Sum? Summy? No, really!
In spite of having been taught (Physical Science!) by one of the very worst teachers ever, whose name was
Winifred and was called
Winnie behind her back, I'll have to go for
Winter simply because it has more interesting sounds and
Winnie or Win are acceptable nns. Plus, a school friend had a Dachshund called
Winnie who was a very nice little dog.