The production of protected cultivation of vegetables could be considered a sustainable solution in arid and semi-arid regions. These regions already suffer from the raising temperature due to the global warming, which represents a great challenge facing our universe nowadays. Hence, the production of vegetables under greenhouse system during the high temperatures may be considered a serious problem in these arid zones due to heat stress. In greenhouses, the production of tomato seedlings should avoid the high temperature stress in particular in arid and semi-arid in summer. The heat stress may cause a lot of troubles for the tomato seedlings in greenhouses in summer starting with the photosynthetic rate, and the metabolism processes in seedlings and in turn the growth and development of these seedlings. Although studies have recognized heat stress on tomato seedlings, research has yet to systematically investigate the effect of heat stress on tomato seedlings in greenhouse in summer under arid and semi-arid regions particularly in developed countries, which their greenhouses have not any climate controllers. Therefore, the management of tomato seedlings may need to address the production problems caused by heat stress in greenhouse conditions particularly in arid and semi-arid zones