When winter is still hanging on outdoors but spring is around the corner, it is time to give summer a flying start indoors.
In warmer zones, a greenhouse or coldframe will be enough shelter. The key is to provide a space that is frost-free, has bright light, and maintains temperatures in the 60's to 70's.
For tomatoes and peppers, optimum germination temperature is 86 degrees. For melons and eggplant, it is a couple of degrees higher. The best way to achieve warm soil temperatures without cooking your seeds or overheating your house or greenhouse is to use heat mats. Typically, they heat the trays that are in direct contact with the mat to 10 degrees above room temperature, making them perfect for germination of seeds indoors.You can still use unheated flats or pots in the house or greenhouse if it is in the 60's or 70's--your plants will germinate and grow more slowly. Some people believe that such plants are more sturdy and pest-resistant.