My DS started at daycare around 9 months ago, and I reckon for the 1st 6 months he was had either a beginning, middle or end of a cold, and if not a cold, then he had gastro. But it does seem to have slowed down a lot over the last couple of months, which I'm assuming is his resilience & immunity starting to kick in. Touch wood, it's probably been at least 3 weeks since either of us had anything, which is a bit of a miracle

FWIW, I also take my DS outside on nice and even not so nice winter days - as long as he's suitably rugged up then I think it's a good thing for him, stops us from getting cabin fever. I don't take him outside if he's obviously sick with temps and/or generally miserable, but as long as he's happy (relatively, for a toddler) I try to find at least a couple of hours a day if we can.