There are at least 4 ways of telling if a colony is alive without opening up the hive:
1. Evidence of cleansing flights on cars or washing
2. Wax crumbs under the hive (need open mesh floor)
3. Dead bees in front of entrance, bees doing housekeeping and throwing out the dead
4. Bees flying
These photos were all shot today in the apiary with a temperature of 8°C.