"Open Winter"?

["Ginny Marr , Tabor Academy 508-748-2000 x263" <GMARR@A1.MEC.MASS.EDU>]

In the middle of a snowless, fairly warm winter in the Northeast, a student
asked if it were true that there were more illnesses than during a cold, snowy
winter.  He's heard his grandmother talk about this being an "open winter." Are
the two related?? Does anyone know any scientific proof of the first question
and the origin/meaning of the phrase?  Please answer me directly and thanks!
        Ginny Marr
        Tabor Academy
        Marion MA 02738
                gmarr@a1.mec.mass.edu