Environment Canada has issued a heat warning for Waterloo Region and surrounding areas ahead of an expected spike in temperatures on Friday that could produce humidex values near 40.

The heat is expected to be short-lived, though, with the weather agency calling for a cold front to sweep through southern Ontario Friday night, bringing temperatures back to normal values for September.

Environment Canada is calling for people, particularly older adults, people with medical conditions, infants and young children and those working outside to stay hydrated and take precautions.

Temperatures are expected to hit a high of 31 C in Waterloo Region on Friday.