It’s also a good way to avoid pests and diseases such as carrot root fly and/or potato blight. These issues tend to occur at certain times of the year. So, if you time sowing crops so that they’re ready to harvest before the pest or disease normally appear, you can benefit considerably.
As well, you have the joy of eating your home-grown harvest earlier than would have been the case if you hadn’t warmed the soil.
Some seeds such as carrots will not germinate if the soil is too cold. On the other hand, others such as lettuce, won’t germinate if temperatures are too high. If unsure, check the instructions on the back of the seed packet.