Does anyone know how to handle a Heat Emergency under the sun's Cancerous Rays?

The mighty US Fed. Emergency Management Agency, FEMA, has guide lines for a Heat Emergency. Could be helpful to avoid a fatal heatstroke or just being more comfortable. I have 20 more tips compared to that benchmark.

The equally mighty American Cancer Society ®  does tell you how to avoid sun induced skin cancer.

Their information is 100 % contradictory with respect to the suggested type of fabric in your clothes!

Learn how to handle hot and sunny weather!


Regarding a Heat Emergency
The US Federal Emergency Management Agency, FEMA's guidelines:"Dress in loose-fitting, lightweight, and light-colored clothes that cover as much skin as possible. Protect face and head by wearing a wide-brimmed hat." "- is based on the most reliable..... information available .... including advances in scientific knowledge... "
 

Is it possible for a non Rocket Scientist to add something to their guidelines regarding dress?
My advice takes you 20 cooling steps, degree by degree, further! Some are techniques.
  Maybe my Master of Science in Applied Physics helped a bit to improve on FEMA'S guidelines.

Regarding Sun and UV Protection against skin cancer
The American Cancer Society ®:Dark colors generally provide more [Sun, UV] protection than light colors. A tightly woven fabric protects better than loosely woven clothing.”