Maybe cover, if you have a super abundance of weeds which are more than can be pulled out, or if your soil is full of weed seeds and likely to germinate en masse. It also depends when you plan to sow or plant – covering may be worthwhile before planting courgettes in May for example.
If you do cover, the rise in temperature is not of much significance for growth after the plastic is removed. Personally I do not cover, my soil is clean and the nutrients are stable.