The 20% Rule OSHA Says New and Returning Workers Should Follow in Extreme Heat

A worker who needs a break in the shade during a hot day, highlighting OSHA’s 20% rule for gradual heat exposure and safer workplace practices – Shutterstock

Hot weather can turn a normal workday into a serious safety challenge, and OSHA’s 20% rule gives new and returning workers a smarter way to adjust. Instead of jumping straight into a full day under blazing temperatures, workers should gradually increase heat exposure so their bodies can adapt.

The idea sounds simple, but it can make a major difference when summer temperatures climb. A worker who returns after time away or starts a new outdoor job needs more than a hard hat and a water bottle. The body needs time to catch up, and rushing that process can create trouble before anyone realizes the heat has taken control.