Late fall winds may tear it. 3 MIL - Nor recommended. Same as 4 mil but usually will not last the full summer. There are several rigid plastics that may be better than these, but they are quite expensive and tricky to use. Do not start with them.
Plants also suffer - growth slows, stops or worse.
Plastic stops winds. In windy locations control of the wind alone may have a great change in plant growth. Even on cloudy days sun rays reach the ground. On very cold winter days, full sun can raise greenhouse temperatures 60 to 90 degrees. Most of the heat is absorbed by plants, soils and other materials.