I paint my hives dark to get more heat here in Maine, even in the
summer when we can have 90 degree days.
If you look at the hive from a heating/cooling point of view, you
have two competing dynamics. The first is the bees want to keep
the hive warm, 95 F for brood health. They also are evaporating
all the water from nectar, which makes for an exceptionally
strong cooling effect. You also have the heat load from the sun,
but even on a 90 degree day, with decent humidity- low dewpoint-
and a good nectar flow, there should be no problems with keeping
the right conditions in the hive. Ventilation, if it is needed,
would be for the same reason as winter ventilation, to get rid of
moisture. So if you have made your hive to have adequate winter
ventilation, you have also set it up for the summer. Our State
Inspector taught me to leave a moisture board on even in the
summer and it works. Moisture is the major problem. In extreme
heat, with little nectar flow bees will bring water into the hive
to evaporate and cool the hive. If there is no place for the
moisture to go, it defeats their efforts.
We tend to think that when we are hot the bees must also be hot,
but I know of few who set their thermostat for 95. The bees
problem is keeping everything warm, at 95, rather than enjoying a
nice 80 degree day.
There is a good writeup on hive temperature and what the bees do
in relation to both hot and cold temps in Hive and the Honey bee.
This thread may have answered a question I have had about my
bees. I never see them clustered at the entrance on hot days or
nights, even with the dark hives. My bet is it is moisture which
leads to high temps that cause clustering. Keep the moisture down
and you keep the temp down. May also answer the question of why
temp control equipment for hives work for some in increased honey
production and not for others. It provides better moisture
control.
Bill T
Bath, ME