Here in the UK tomatoes can be grown out of doors or in unheated greenhouses from June to mid October. Heat is needed to produce tomatoes outside of this season.
I was shocked to read, in this week’s Riverford newsletter, that growing tomatoes in heated glass houses releases 2 Kg of carbon dioxide for every 1Kg of tomatoes produced! Transporting tomatoes by truck from places like Spain and Italy where tomatoes can be grown without heat during the winter produces 1/10th of the carbon dioxide emissions of producing tomatoes here in the UK in heated polytunnels. So if you are going to buy tomatoes out of season it’s more environmentally friendly to buy one’s from southern Europe that home grown.