These hot days also invite line noise via inrush spikes from all of the cooling devices down stream, like AC units, but also refrigerators, freezers, dehumidifiers and stuff like that. Some have poor power supplies that may introduce DC voltage into the line, which can raise hell with HiFi equipment in general, usually resulting in some "pops" or other nasties, and even induce some nasty hum in some transformers.
Wayner