Protection from Frost
In spring, a greenhouse heats up quickly but also cools down quickly. With proper preparation, tomatoes can be protected from unexpected cold snaps.
Heat Accumulators
Water, stones, concrete, and other dark surfaces absorb heat well. Place covered black barrels of water – the larger, the better.
Soil also heats up, but in the evening, it evaporates moisture along with heat. Cover it with black film (with mulch underneath); it will absorb heat during the day and block evaporation in the evening. The film should be removed when hot weather arrives.
Source: pomidorai.eu