What is a heatwave?

a) Unusually cold weather conditions
b) Extended period of excessive heat
c) Strong winds and storms
d) Heavy rainfall and flooding

A heat wave, or heatwave, or extreme heat, is a period of abnormally hot weather. It is often accompanied by high humidity, especially in oceanic climate countries. While definitions vary, a heat wave is usually measured relative to the usual climate in the area and relative to normal temperatures for the season.