Yes it is scary. We get incidences on hikes regularly. Managed correctly and caught early enough is fine. We have had to helicopter one guy out though. Generally, I've found heatstroke mainly affecting non-locals, usually either at the beginning of summer or after cool weather (ie they just arrived, it got cool, not been exercising in the heat for a while) or while doing severe exertion (ie running in the middle of the day).
It's not a reason to sit inside all summer though. Take precautions, act on symptom, carry enough water and build up to it gradually and you will be fine. Never hike alone though because all of the above is much easier with folks to help you.
In high humidity it can be difficult to replace lost fluids, so make sure you're well hydrated before you even step out of the house. I go through a gallon in two hours if I'm working out hard in the heat, and usually buy another bottle or two after I'm done.
Last edited by emx; 20-06-2013 at 06:04 PM.
Uniqlo undershirts = best tip
I jump into a mountain creek to cool down before I go back home
Eat only cool foods, like fruit, raw veg, sushi. Drink loads of cold water and turn off the hot water and stick to cool showers. I find that the water in the pipes is hot enough that I don't need to turn the heating on. Wide brim hat, loose cotton clothing in light colours to deflect the heat.
Frozen daiquiris, frozen margaritas, 7-11 slurpees.....