What the heck are all you people talking about! It is STILL winter here! We had 4 inches of snow yesterday and last year it snowed on JUNE 6!
To date, I have lost 3 of 6. The three lost were the weakest going in. Two starved out. The last one was more directly my fault (which is most upsetting). I put dry sugar on them because they were out of food - but didn't notice that the newspaper was covering the entire top. As a result, there was little/no ventilation, they got wet. Two weeks later when I checked, they were dead. It happened with a second hive also, but I caught it and cleaned it up. Hopefully, they recovered.
For what it is worth, of my remaining hives, the two strongest both had screened bottom boards all winter. The hives with solid bottoms died first. All other equipment (lids, hive wraps, etc.) were the same (populations going in did differ).
Next year, they will all have screened bottom boards.