From Longman Dictionary of Contemporary Englishheat waveˈheat wave noun [countable] DNa period of unusually hot weather, especially one that continues for a long time OPP cold spell
Examples from the Corpus
heat wave• Early in August a heat wave hit.• I remember we arrived during a heat wave and had to go into this refrigerator where they kept the furs.• She shivered at the memory of the horrors that had accompanied that awful heat wave.• People were saying that a cold spring meant an early heat wave in summer.• A great heat wave descended; it was a beautiful day, the sun turned red at three.• Ideas flowed out of me like water out of a Brooklyn fire hydrant in the midst of a summer heat wave. 