Guide

Indoor heat rules for warehouses

Is there a legal maximum temperature for a warehouse?

In most jurisdictions, no. There is no federal US maximum, and neither the UK nor Australia sets one. What several rules do require is assessment and control above a trigger — California's indoor heat standard, for example, applies from 82°F indoors, with more required at 87°F. Check the rule for your own state or country.

Starting with the limitation

This site is built around an app that reads outdoor weather data. It cannot tell you how hot it is inside a warehouse, and no amount of modelling would fix that: the roof, the insulation, the ventilation, the racking layout and the forklift traffic are all invisible to a weather station.

So the honest structure for this page is: here is what the rules require, and here is what you need to measure it, which is not this app.

What the rules actually do

Nobody sets a maximum. What the better rules do instead is set a trigger above which assessment and controls are required.

Three jurisdictions, three shapes. Verify current text before relying on any of it.
Where	Maximum?	What applies instead
California	No	Indoor heat illness prevention standard from 82°F indoors, with further requirements at 87°F — or at 82°F where clothing restricts heat removal or workers are near radiant heat
US federal	No	General duty clause; a specific heat rule at proposal stage
UK	No	A duty to provide a reasonable temperature, discharged through risk assessment

The reason regulators resist a maximum is not indifference. It is that air temperature alone genuinely does not determine heat strain: humidity, air movement, radiant heat, clothing and workload all matter, and a single number would be simultaneously too strict for a seated inspector and far too lenient for someone stacking pallets in a Tyvek suit.

Why warehouses in particular

Three structural reasons the demand for this question is real:

Roof gain with nowhere to go. A large, dark, poorly insulated roof is a radiant panel over the whole floor. The load arrives from above all afternoon.
Stratification. Hot air rises, so mezzanines and upper racking run hotter than the floor — often several degrees. A thermometer by the office door measures the coolest part of the building.
Thermal lag. The building keeps radiating into the evening, so a late shift can be working in the hottest conditions of the day, hours after the outdoor peak.

What to measure, and where

WBGT with a globe, if radiant heat is significant — and under a hot roof it is. A plain thermometer cannot see radiation, which is exactly the load a warehouse has most of. App or WBGT meter covers what to look for in an instrument.
At the work locations, including the worst ones. Upper racking, mezzanines, near equipment, inside trailers being unloaded.
At the right time. Mid-to-late afternoon, and again on the late shift if there is one.
With the workload written down beside it, because every published limit has a workload axis. Run the work/rest calculator once you have a measured WBGT.

What this site can help with

The outdoor half. Loading bays, yards, deliveries and anyone working outside the building are all questions the heat index calculator and WBGT estimator can help with — and on a hot day the yard crew and the racking crew have genuinely different problems.

For the enforceable-versus-proposed picture in the US, OSHA and heat. For the question as workers usually ask it, too hot to work?

Common questions

What temperature is too hot to work indoors?

No jurisdiction sets a general maximum. California's indoor heat illness prevention standard takes effect at an indoor temperature of 82°F, with additional requirements including cool-down areas and assessment at 87°F, or 82°F where workers wear clothing that restricts heat removal or work near radiant heat sources. Those are trigger points for action, not a point at which work must stop.

Does the UK have a maximum workplace temperature?

No. The Workplace Regulations require a reasonable temperature and the Health and Safety Executive declines to set an upper figure, on the grounds that thermal comfort depends on humidity, air movement, radiant heat, clothing and workload rather than air temperature alone. The duty is a risk assessment.

Why is a warehouse hotter than outside?

Roof solar gain with no way out. A large uninsulated or dark roof absorbs sun all day and radiates downwards; the air stratifies so the mezzanine and upper racking are hotter still; and equipment, lighting and vehicles add heat. Warehouses commonly run several degrees above the outdoor air by mid-afternoon, and they cool down more slowly in the evening.

What should an indoor heat assessment measure?

Temperature and humidity at minimum, and ideally WBGT with a globe, because radiant heat from a roof or a furnace is a large part of the load and a plain thermometer cannot see it. Measure where people actually work, including the worst spots — upper racking, mezzanines, near ovens or presses — not by the door.

Does the heat index apply indoors?

Cautiously. The equation will produce a number from any temperature and humidity, but the published risk bands assume outdoor exposure with some air movement. A still, unventilated indoor space at the same readings is worse than the band suggests, which is one reason indoor rules tend to use plain temperature triggers plus an assessment rather than a heat-index band.

Sources

Published 30 July 2026