When someone is having a heat stroke especially one with severe heat stress, call or have someone to call an immediate medical assistance as you do the following...
Take the person having a heat stroke to a shady area and have him lay relaxed.
Fan him or her rapidly especially using wet material. In severe cases you might need to sprinkle some drops of cool water on the individual and continue fanning.
You can dip the person in a cool shower or a pool without drowning him. A tube may have similar function.
If you can't find any of the above, deep a fabric in a cool water and sponge the person.
What to Do When Someone is Having a Heat Stroke: Stop cooling as soon as the body temperature drops to 101°–102°F.