Answer: Hooray for you! Composting is a great source of organic matter and nutrients for the garden.
Chances are that you will not have enough heavy rains in your part of Illinois to warrant keeping your pile covered all the time. You might construct some sort of temporary cover to put on during heavy spring rains, but the rest of the time you will need the moisture to keep the pile working. In fact, during the heat of the summer you may need to use plastic to keep moisture in since wire bins allow quite a bit of drying out. Remember, you want the materials to be moist enough that when you squeeze them, they stick together a bit, but not so wet that you can squeeze water out.
After your compost has finished, further soaking will begin to leach away the nutrients you've worked so hard for, so again, you may want to put on some sort of lid to divert rain from the finished compost until you can get it onto the garden.
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