It was pretty rough to continually find my hives dead last winter but the hives are in much better health this year.Sorry to hear that. I've heard of some sort of disease hitting bee keepers locally here.
It's definitely a two-edged sword. The cold over this way is doing its part to keep some of the invasive species in check. We had a 0 degree night in January 2018 and several nights below 10 these past two winters which really helps with some of the imported and invasive Asian plants.