It is very tempting to open the hive and disturb the brood nest when the first sunny days of spring arrive. It is perfectly OK to have a quick peep to make sure that all is well but unless the weather is really warm for this time of the year the first thorough inspection should be left until April. A warm day in March is a good time to replace the hive floors with clean ones. This can be done with little disturbance to the bees. A good rule is that hives should only be opened when it is warm enough for the beekeeper to be wearing shirt sleeves.