Guide
OSHA’s proposed heat triggers: 80°F and 90°F
Updated 2026-07-10
Quick answer
OSHA’s proposed federal heat rule (not yet final) sets two heat-index trigger points: 80°F, an “initial heat trigger” requiring water, shade or cooling, and rest breaks; and 90°F, a “high-heat trigger” adding more frequent breaks and closer monitoring. As of this writing OSHA has set no target date for a final rule.
Swelter is not affiliated with OSHA
Swelter is an independent, privately developed app. It is not affiliated with, endorsed by, or connected to OSHA, NIOSH, CDC, or the National Weather Service. This page summarizes OSHA’s own published proposal in plain language and links to the source — it is not legal or compliance advice.
What the two triggers mean
OSHA’s Notice of Proposed Rulemaking for Heat Injury and Illness Prevention describes two heat-index thresholds. At 80°F, the proposed “initial heat trigger” would require employers to provide drinking water, break areas with shade or cooling, and a way for new or returning workers to acclimatize. At 90°F, the proposed “high-heat trigger” would add mandatory rest breaks at a set frequency and closer supervision for signs of heat illness. These are the same numbers Swelter marks on its live gauge.
The rulemaking is proposed, not final
OSHA published this proposal on August 30, 2024. The informal public hearing concluded in July 2025, and the post-hearing public comment period closed in October 2025. As of this writing, OSHA has announced no target date for issuing a final rule. Until a final rule is published and takes effect, these numbers are a proposal, not a legal requirement — always check OSHA’s own rulemaking page for the current status.
Water, rest, shade — the general idea
Independent of any final rule, water/rest/shade is the widely cited baseline for reducing heat-related illness during outdoor work: accessible drinking water, scheduled rest breaks in shade or cooling, and a gradual acclimatization period for anyone new to heat exposure or returning after time away. This is general public-health guidance, not a promise that following it prevents illness in any individual case.
Not affiliated with, endorsed by, or connected to OSHA, NIOSH, CDC, or the National Weather Service. Threshold values and guidance are based on their published public information. Swelter is an informational tool, not a medical device. It does not diagnose or prevent heat illness.