Well here are the #'s there is some small amount of variance.
code:
Season SumL(44) SprH(7) WinW(13) FallB (53)
Early Summer 44 8 13 39
Mid Summer 55 7 11 53
Late Summer 55 7 10 53
Early Fall 55 7 9 53
Mid Fall 49 6 13 66
Late Fall 46 5 13 66
Early Winter 45 5 13 66
Mid Winter 39 7 16 59
Late Winter 36 7 16 56
Early Spring 34 7 16 54
Mid Spring 44 8 14 46
Late Spring 44 8 13 42
So For SL's it was 25% Maximum Loss and Gain for on and off seasons. The Spring Hawk lost 28.57% of it's HP in off season (5) and only gained 14.2% (Could have been a bad year for Spring Hawks). Winter Wolves gained 23.1% and lost 30.7% (Bad year for Wolves too). Fall Bear gained 24.5% and lost 20.7% in it's bad time. So I unless they are coded differently, it seems to be able to vary quite a bit.
Damn you Gandalf for making me answer my own question!