Stelvio, Gavia, etc. Time of Year?

Stelvio, Gavia, and Mortirolo - can they be done in mid-late May on a bicycle?
Early June?
Mid June?
Airfare gets expensive in late May and June so am hoping roads and passes out of Bormio are doable.
Thanks -

take care, in may it could still snow (the Giro with the snow wasn't that uncommon...).

better in july; in august it often rains during the afternoon, but it's the hottest month. In september...the weather up there is simply perfect, why don't you consider september?