You are right - pumpkins, as well as squash, gourds, and cucumbers, will mature early with the weather conditions you describe. It does present a problem of storing the pumpkins until they are ready to use, but you should be able to keep them until Halloween. There are two ways to maintain your pumpkins until then.
1. Keep them on the growing vines, as long as the vines and pumpkins are healthy, until the first light frost. Then harvest your pumpkins and store them in a clean, dry space that is cool with some humidity. The universities of Illinois and Ohio recommend temperatures between 50 and 55 degrees F, with average to high average humidity (50 to 60 percent).
2. Harvest earlier if your pumpkins are fully ripe - if the color is a solid, deep orange and the rind is hard. Cure them for two to three weeks in a room that maintains a temperature of 75 degrees F. Then move them to 50 to 60 degrees F storage in a clean, dry space, such as a cool basement area.
