nice and cool, mild and comfortable
泠 centers on a pleasant, gentle coolness: a mild, comfortable temperature that feels refreshing rather than harsh.
泠 combines 氵 (water) with 令, which likely contributes the sound. The water component suggests a cool, refreshing quality.
Water 氵 beside the commanding 令 shape: imagine a gentle stream of cool water ordered to stay mild and refreshing.
For レイ, picture a cool lake under a gentle ray of sun: ray -> レイ, and the water stays nice and cool.