When making fudge or any candy that requires a thermometer or testing to find "soft-ball stage" or "hard ball stage", the weather DOES play into the results. If the air is dry you need to add more moisture in some cooking (like bread) or if it's wet out, then reduce the moisture.
ALSO -- and I burned 3 pans of fudge before I figured this out....if you live at HIGH altitudes, the temps on the thermometer need to be LOWER than what recipes call for. In another words...if the recipe says cook to 325 degrees, then cook it to the 320 degree temp. HIGH or LOW altitude DOES make a difference!