I had a similar experience last year. I was getting a lot of flats in February and March and blaming it on the cold weather.

One day I chanced to look at all my punctured tubes and discovered they were all punctured in the same spot. That lead me to investigate the tire which has a small tear in the sidewall, which -- out on the road -- would pinch the tube.

I bought two new Schwalbe marathon tires and haven't had a flat since.

So, follow the advice from those above:
- check the tire very closely
- check the rim and tape.

It's most likely one of those.