Anaheim peppers are moderately hot, although their heat depends on where they’re grown and how mature they are. Varieties of the pepper grown in New Mexico tend to be hotter than those grown in California, and the mature red ones tend to be hotter than the green. The Anaheim chile varies from light green to dark green to red and grows to between 6 and 10 inches (15–25cm) long and 1 to 2 inches (2.5–5cm) around.
The hotness of peppers is measured in Scoville heat units, and Anaheims have a heat score that ranges between 500 and 2,500. How high a chile pepper scores on the heat scale is determined by high-performance liquid chromatography measurement of parts per million capsaicin. This figure is then converted into the historic Scoville heat units that signify how much dilution is necessary to drown out the chile’s heat.