To turn the oven on so it has time to come up to the desired cooking temperature. For years it was assumed it would generally take 20 minutes for an oven to reach the cooking temperature. Testing has shown most modern gas and electric ovens can do this in 8 minutes. Further testing has shown that cooking food in a cold oven for the same time as in a preheat one, showed no difference in the finished product.
Season: available year-round