Two major organizations that represent local authorities across the U.S. have voiced their support for a bipartisan bill that would open the door to federal aid for extreme heat.
This article didn't even mention deadly wet bulb conditions (ie, humidity so high that sweating no longer cools a person down).
We'll be hearing more and more about that as climate change progresses. Talk about a disaster... combine that with a power failure, and you'll start seeing a true catastrophe.
This prompted me to look up how humidity percentages work. It's the amount of water in the air relative to it's current maximum based on temperature and pressure. Going above 100% is possible above 25000 ft due to the purity of the air. Clouds formed when impurities are introduced or pressure and temperature allow. (This is all just my cursory pleb 'knowledge' and may be partially or entirely wrong)