A period of abnormally and uncomfortably hot weather. It could last from several days to several weeks. The Weather Channel uses the following criteria for a heat wave: a minimum of ten states must have 90°F plus temperatures and the temperatures must be at least five degrees above normal in parts of that area for at least two days or more.
HEAT WAVE
Meaning of HEAT WAVE in English
Weather and meteorology English vocabulary. Английский словарь погоды и метеорологии . 2012