For your client who is training outside in 90癋 (32癈) weather at a moderate intensity, how often should they drink water?

ACSM fluid replacement guidelines recommend consuming 6-12 oz of fluid every 15-20 minutes during exercise, with frequency increasing in hot environments where sweat rate is elevated. At 90 F (32 C), heat stress accelerates fluid loss significantly, and a 15-minute interval ensures the client stays ahead of dehydration rather than trying to catch up after significant losses have occurred.

A 30-minute interval may be adequate in temperate conditions but is insufficient in 90-degree heat where sweat rate can exceed 1 liter per hour at moderate intensity.

Drinking only every 60 minutes during hot-weather exercise would allow clinically significant dehydration to develop, impairing performance and increasing heat illness risk.

Thirst is a lagging indicator of hydration status - the sensation of thirst does not appear until an individual has already lost 1-2% of body weight in fluid, at which point performance and thermoregulation are already compromised.