In cold climates honey bees stop flying when the temperature drops below about 10 °C (50 °F) and crowd into the central area of the hive to form a "winter cluster". The worker bees huddle around the queen bee at the center of the cluster, shivering in order to keep the center between 27 °C at the start of winter (during the brood-less period) and 34 °C once the queen resumes laying. The worker bees rotate through the cluster from the outside to the inside so that no bee gets too cold. The outside edges of the cluster stay at about 8–9 °C (46–48 °F). The colder the weather is outside, the more compact the cluster becomes. During winter, they consume their stored honey to produce body heat. The amount of honey consumed during the winter is a function of winter length and severity but ranges in temperate climates from 30 to 100 lbs./colony. If the colonies are protected with insulation and wind breaks, conditions inside the hive improve and the bees don’t need as much honey to survive. Not only do the bees fair better, but there is more honey left in the spring. The more material (wood, insulation, etc.) there is above brood boxes, the better the chance that moisture buildup will be reduced, increasing bee survival.