Warming the Soil in the Pumpkin Patch

If I can get my hoop houses (little greenhouses) put together this week I'd like to get my plants in the ground this coming Saturday.  To get the soil heated up in the planting area I've put down clear plastic over the soil to help warm it up.  With the clear plastic, as long as it isn't too hot outside, the soil will warm up to almost 80 degrees which the pumpkin plants will like because they don't care to be transplanted into cold soil.  It has been so warm in Denver that it cold soil shouldn't be a problem this year.