Greenhouses In the countryside of Estonia, my guesstimate is about 50 percent of the homes have a greenhouse. The weather here is Sweden level; there is a time of 6 months with lot of light and a time of 6 months of lots of dark. Even though I am very far north, the ever-present sun would keep a greenhouse warm. The days have about 20 hours of sunlight right now or more, this creates a long day of sun to heat the place. An effect I have never considered before, if the sun shines for 20 hours is the mean temperature higher.