Frequently asked questions
Straight answers, no marketing gloss
The most important things to know before you download — including what Swelter is not.
Is Swelter affiliated with OSHA, NIOSH, CDC, or the National Weather Service?+
No. Swelter is an independently developed app. It is not affiliated with, endorsed by, or connected to OSHA, NIOSH, CDC, or the National Weather Service. The heat index formula and the 80°F/90°F markers are based on their published public information.
Is the WBGT number a real measurement?+
No — it’s an estimate. A true WBGT reading needs a physical black-globe thermometer in direct sun and wind. Swelter’s Pro WBGT figure is a software estimate from available weather data, always labeled as an estimate, and it is not a substitute for an on-site WBGT meter.
Is Swelter a medical device?+
No. Swelter is an informational tool, not a medical device. It computes a public, published heat-index formula and shows the NWS risk bands — it does not diagnose, treat, or guarantee anyone’s safety.
Does Swelter work without a network connection?+
Yes. The free core works fully offline: type in a temperature and relative humidity and Swelter computes the heat index, risk band, and 80°F/90°F markers with zero network access. An optional weather lookup can fill temperature and humidity in automatically when you have a connection.
What does the one-time Pro purchase unlock?+
Exactly four things: the WBGT estimate, a Home/Lock Screen widget, threshold alerts on the 80°F and 90°F triggers, and a private, on-device heat log with CSV export. It is a single one-time purchase — never a subscription.
Is OSHA’s heat rule already in effect?+
No. As of this writing, OSHA’s federal heat rule is a proposal (Notice of Proposed Rulemaking, published August 2024). The public hearing and comment period have closed, but OSHA has announced no date for a final rule. Swelter always labels the 80°F/90°F markers as “OSHA-proposed.”
Where does Swelter get its weather data?+
From api.weather.gov, the National Weather Service’s public API — the only network request the app makes, and it is optional. Location is used on-device to make that request; nothing about your readings is sent to us, because there is no backend.
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. In an emergency, call 911 or seek medical help — this app is not a substitute for either.