humid
溽 centers on oppressive, sticky humidity: the kind of damp, muggy heat that makes the air feel heavy and uncomfortable.
溽 combines 氵 (water) with 辱, which likely contributes the sound and the idea of something heavy or oppressive, together suggesting damp, muggy conditions.
Water (氵) plus the heavy, oppressive feel of 辱: imagine a thick, wet blanket of humidity pressing down on you, making the air feel muggy and hard to breathe.
For ヒョク, picture a humid day so sticky that you feel like you're wrapped in a heavy, damp hyo-ku (a made-up word for a humid cloak): hyo-ku -> ヒョク, and the water radical 氵 reinforces the dampness.
sultry; muggy; steamy; sticky; hot and humid