Excessively hot and humid or marked by sweating and faintness:
— A sweltering room.
— Sweltering athletes.

synonym: sweltry.

Roget 382: hot, warm, mild, genial, tepid, lukewarm, unfrozen; thermal, thermic; calorific; fervent, fervid; ardent; aglow.    sunny, torrid, tropical, estival^†, canicular^†, steamy; close, sultry, stifling, stuffy, suffocating, oppressive; reeking etc. v.; baking etc. 384.    red hot, white hot, smoking hot, burning etc. v.. hot, piping hot; like a furnace, like an oven; burning, hot as fire, hot as pepper; hot enough to roast an ox, hot enough to boil an egg.    fiery; incandescent, incalescent^†; candent^†, ebullient, glowing, smoking; live; on fire; dazzling etc. v.; in flames, blazing, in a blaze; alight, afire, ablaze; unquenched, unextinguished^†; smoldering; in a heat, in a glow, in a fever, in a perspiration, in a sweat; sudorific^†; sweltering, sweltered; blood hot, blood warm; warm as a toast, warm as wool.    volcanic, plutonic, igneous; isothermal^†, isothermic^†, isotheral^†.    ... show more