October 7 is the average date of the first fall freeze in Denver so it should be no surprise that a freeze advisory is issued for tonight, October 2. The earliest fall freeze was September 8 in 1962 and latest November 15 in 1944.
Some of your gardens may have been nipped when it got down to 33 degrees F last month on September 11, particularly those on the northern part of the Front Range (Fort Collins, etc.). Often we have warm temperatures after these episodes as we have had for the rest of September. Indeed, daytime temperatures are predicted to be in the mid 70's by the weekend two days from now and reach the 80's by midweek.
With these short one or two night possibilities of a freeze it is worthwhile to cover frost-tender vegetables such as tomatoes, peppers, squash, etc particularly as we get near the average first fall frost date. Use covers to trap heat stored in the soil around plants as was done in the photo. A sheet of plastic or fabric will serve as long as the material is not too heavy to break down plants.
In the photo, double frost protection was used, probably overkill for this early in the season when it has been warm. A poly frost blanket (thick floating row cover fabric) was thrown over the tomato cages and then plastic placed over top and sealed into the soil to trap heat like an enclosed greenhouse. Clothes pins were used to keep the plastic from flapping in the wind.
Invent your own frost protection cover out of materials you have on hand. Just remember to uncover or at least ventilate the next morning as sun will soon cook plants covered tightly with plastic.
Photo credit: Temporary frost cover over tomato cages - Carl Wilson