It is supposed to get to 94 degrees today in Denver. Anything above about 91 degrees pretty much shuts pumpkin plants down growth wise because the plant is just trying to keep up the evaporative transpiration going on. When the pumpkins are growing you will see 1/2 inch of growth during the daytime when it is above 91 degrees and see 2-3 inches at night. Colorado's hot days and cool nights aren't ideal for growing giant pumpkins so you have to try to create an environment that makes them think they are in Iowa or Ohio.
I have a 14% shade hail netting cloth over my patch. That helps reduce the heat a little in the patch and reduce Denver's leaf damaging high UV rays. I also have the sprinkler system set on a timer so the plants get misted throughout the day so the leaves get cooled off and the humidity is a little higher.
Since my plants aren't quite ready to come out of the hoop houses I've covered the hoop houses with white sheets to help reduce the heat and I have the hoop houses fully opened up today.