Don't know if you've already gone or not gone, but if you don't feel well you should never run when ill. It'll always take longer for your body I recover. (Read this in my running magazine)
However if you feel okay, should still try stick to your commitments as it can be a sticky spiral to go down if you make one excuse, other less valid ones can stop you too =)
I ran in the pouring rain yesterday, but had head warmer, two hoods on and thick trousers. Touchwood...no illness yet! Perhaps I'm just lucky!