It's an aerial problem.
Received signal strengths don't remain constant. They're affected by seasonal changes to the ionospheric layer, the 11-year sunspot cycle, solar flares, signal path obstructions (such as trees growing or shedding their leaves, new buildings being constructed, or weather conditions such as rain or snow) plus loads of other things.
Something has adversely affected the strength of the signal recived by your aerial, so that it's no longer able to 'pull in' some channels. (Ideally, the elements of an aerial should be exactly the right length to 'resonate' with the incoming signal. Since every channel is on a different frequency, this is not possible. So, inevitably every aerial will be better matched to some channels than to others).
Given the recent weather conditions, the most likely cause of the problem is that the aerial has been knocked out of alignment by the wind (or, possibly, rain and snow have given rise to water ingress in an electrical connection). Unless you're confident working at the top of a ladder (or you've got a mate who is) your only option is to call in an aerial fitter.
Chris