Hello, Carolyn, When I grow jalapenos, I usually wait until they are about 3" long and have some black coloration around the shoulders. I have found that the weather definitely influences the Scoville factor in jalapenos: the hotter the weather, the higher the Scoville rating. For instance: in November, my jalapenos are so mild that they could be substituted for bell peppers in recipes; that is NOT the case in August! When the jalapenos turn red, there is a nice fruitness with the heat, a fruititness that is absent when they are green. Enjoy! Ron Van Nuys, CA