Pumpkins in June?

We compost around here and so when my husband planted our grapes during early spring we used compost. When things started heating up we found that we were going to have some sort of squash. So we retransplanted them and nourished them. Imagine my surprise when I found a pumpkin! I've tried to grow pumpkins in Phoenix for years now and the year I don't try I actually get one. How fun. To bad it came up in June instead of October!