Heat exhaustion
Heat exhaustion, which could lead to heatstroke, was a condition in which an individual was taking in more heat than he or she could handle. A Human who suffered from heat exhaustion would experience dehydration, various delusions including hallucinations, and fatigue.

In 2152, Commander Tucker suffered from heat exhaustion while stranded with Captain Archer on the desert surface of the Torothan homeworld. ()

To explain the lack of transportation while visiting the Skagaran colony planet in 2153, T'Pol and Tucker explained that their horses had perished several miles north of town from heat exhaustion. ()

Symptoms of heat exhaustion
Symptoms of heat exhaustion can include:
 Dizziness
 Feeling faint
 Visual hallucinations
 Confusion
 Dehydration
 Nausea
 Headache

External links 
 
 

Medical conditions