Learn how to say Swelters correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word swelter:
(intransitive) to suffer under oppressive heat, esp to sweat and feel faint
(transitive) (archaic) to exude (venom)
(transitive) (rare) to cause to suffer under oppressive heat
a sweltering condition (esp in the phrase in a swelter)
oppressive humid heat