NEW: This update adds new widgets for your home and lock screen. The flagship new widget for your Home Screen is a new full color gradient widget which shows the current WBGT and coach verdict. GOOD TO GO? Or caution, high risk, cancel, etc. now rendered in beautiful full color, with a more minimalist layout than some of the more information dense widgets. We also added a handful of new information dense widgets if you want more info at a glance: “Now & Best Window” - a widget which combines current conditions along with today’s best window. And “Heat index” widgets for viewing the current air temp / humidity. Also new: 2 widgets for your lock screen. A small and large variant of the same Heat Index widget, which is calculated from the current air temperature / humidity, and shows how hot the air feels at rest in the shade. The Heat Index widgets follow the same dynamic system that the app itself uses. When it is hot outside the heat index is displayed, when it’s comfortable this switches to showing the “feels-like” temp. And in cold, windy conditions, this displays the wind chill.

NEW: Heat Stress Guidance. Tap "Additional Guidance" under the coach sentence to see published NWS guidance for your current reading, including how quickly heat stress builds in direct sun and how many minutes of breaks to take each hour. The WBGT gauge now places its marker more precisely within each color band. Located and fixed a difficult to reproduce bug, on some small screen devices, the X-axis could overflow, leading to the screen becoming horizontally scrollable. We fixed this by ensuring X-axis scroll is never possible. If you run into this or similar bugs/issues, please email me at gavin@rbrn-labs.com

Small enhancements to keep the app running smoothly.

Small update to the science: WBGT readings during sunny hours now run a touch higher (up to about 1°F / 0.5°C); nights and cloudy hours are unchanged. We tuned the WBGT algorithm slightly to account for weather forecast data inputs. The globe temperature term now follows spherical geometry instead of a horizontal-surface sine, the Kasten-Czeplak cloud coefficient was recalibrated very slightly, and the wind cooling credit was modulated so that it now fades under strong sun, not just high humidity. Every change was replayed against tens of thousands of station-hours we have banked. These come from the same WBGT monitoring network we compare against. The end result: sunny hours now read a touch higher; most readings are unchanged. The difference is simply a very marginal increase in WBGT during very sunny hours. We continue to refine our algorithm against weather station data, and in-the-field reports from athletes using the app! Core accuracy holds: across more than 20,000 compared station-hours, readings average within 0.7°F (0.4°C) of the monitoring network, with 90% exact flag agreement and 99.96% within one flag. The app shows a "Near" line whenever a reading sits close to a boundary.

Fixed a cosmetic bug with temperature readings displayed in Celsius. Small refinements to the heat index / feels like / wind chill labels in the app.

Added a new Heat Index card to the Today screen. It uses our new dynamic tri-state label system. At 80°F and above, the number is the NWS heat index. Below that, it is the feels-like temperature. And in cold, windy conditions (below 50°F with wind above 3 mph), it becomes the wind chill. Anywhere you see this number in the app or widgets, the label now matches the conditions: Heat Index when it is hot, Feels Like when it is comfortable, Wind Chill when it is cold. Added a quick-glance precipitation chance tile to the Today screen. Improved the weather condition icon colors in light mode. Fixed a crash in the Mac version of Swelter when opening the location picker or the upgrade screen. Several other small fixes and improvements throughout the app.

Introducing a major new feature: Swelter now integrates with Siri & Shortcuts. Ask Siri for current heat conditions and Siri will reply with the current heat risk and WBGT from the app's forecast data. Power users can build custom Shortcuts using the WBGT and heat risk flag data. v1.4.5 adds support for meters per second (m/s) in the Units settings for wind speed.

Introducing a major new feature: Swelter now integrates with Siri & Shortcuts. Ask Siri for current heat conditions and Siri will reply with the current heat risk and WBGT from the app's forecast data. Power users can build custom Shortcuts using the WBGT and heat risk flag data. v1.4.5 improves how Swelter works around the world. There is a new Units screen in Settings. You can now choose your wind speed unit (mph or km/h) separately from your temperature unit (°F or °C), so the app can match the way your region reads the weather. Swelter also now fully supports 24-hour time. Every time shown in the app follows your device's 12-hour or 24-hour clock setting.

Introducing a major new feature: Swelter now integrates with Siri & Shortcuts. Ask Siri for current heat conditions and Siri will reply with the current heat risk and WBGT from the app's forecast data. Power users can build custom Shortcuts using the WBGT and heat risk flag data. v1.4.3 brings a new feature for Pro users. Tap the Week tab and there is a new 10 Day Forecast button which lets you view weather conditions, high/low air temp, and peak WBGT + heat risk for the next 10 days! This is useful for seeing upcoming temperature trends and heat waves. Further out forecasts may change and update. v1.4.4 Includes a few minor refinements to the Guide screen.

Introducing a major new feature: Swelter now integrates with Siri & Shortcuts. Ask Siri for current heat conditions and Siri will reply with the current heat risk and WBGT from the app's forecast data. Power users can build custom Shortcuts using the WBGT and heat risk flag data. v1.4.3 brings a new feature for Pro users. Tap the Week tab and there is a new 10 Day Forecast button which lets you view weather conditions, high/low air temp, and peak WBGT + heat risk for the next 10 days! This is useful for seeing upcoming temperature trends and heat waves. Further out forecasts may change and update.

Introducing a major new feature: Swelter now integrates with Siri & Shortcuts. Ask Siri for current heat conditions and Siri will reply with the current heat risk and WBGT from the app's forecast data. Power users can build custom Shortcuts using the WBGT and heat risk flag data. v1.4.1 brings a new heat index chart to the Week tab for Pro users. You can now view the heat index for the week ahead, to track how hot the air feels. v1.4.2 brings improvements to the Today screen. The UV index chart no longer shows empty gray bars for UV 0, and there is a new cloud cover chart which shows how overcast or clear today's skies are.

Introducing a major new feature: Swelter now integrates with Siri & Shortcuts. Ask Siri for current heat conditions and Siri will reply with the current heat risk and WBGT from the app's forecast data. Power users can build custom Shortcuts using the WBGT and heat risk flag data. v1.4.1 brings a new heat index chart to the Week tab for Pro users. You can now view the heat index for the week ahead, to track how hot the air feels.

Introducing a major new feature: Swelter now integrates with Siri & Shortcuts. Ask Siri for current heat conditions and Siri will reply with the current heat risk and WBGT from the app's forecast data. Power users can build custom Shortcuts using the WBGT and heat risk flag data. Sources & Algorithm screen updated with insights into how Swelter calculates heat index. Improved WBGT accuracy under cloud cover. Our latest validation studies against measured weather-station data showed cloudy hours reading slightly low (by about 1 °F), so we tuned how Swelter converts cloud cover into sun strength. Most readings are unchanged; the improvement shows up during mid-day hours under heavy cloud cover. Bug fix: In frigid conditions the WBGT calculator now opens within proper bounds.

Improved the yellow text color used in many spots across in the app in light mode. This color is now easier to read in light mode, matching the contrast ratio used for the dark mode variant. This fix applies to the widgets as well.

Completely reworked the in-app guide to be easier to follow and more useful. Minor refinements to various UI elements throughout the app. Above 80F the "feels like" temperature now renders with the label "HEAT INDEX" - this is the official start of heat index scale (>80F), and Swelter now surfaces this label more cleanly. Fixed a bug where the heat risk (WBGT) calculator loaded with the incorrect cloud cover %

New feature: The WBGT calculator. Set your own temperature, humidity, sun, and wind readings, and Swelter estimates the WBGT and its risk flag. Find it at the bottom of the Today screen (Pro feature). Minor refresh to light mode app icon, a new Guide section, and updated validation numbers.

Added a new storm indicator on the "Heat Risk - Next Hours" widget at the bottom of the Today screen. You can now easily see storms ahead. The "Try the Algorithm" feature (Settings > About > Sources & Algorithm) now functions as a proper WBGT calculator. You can drag sliders between the normal WBGT range (40°F to 120°F air temperature) along with humidity, sun angle, cloud cover, and wind to calculate WBGT from your own readings. Several small stability enhancements. Thank you for using Swelter! We have a bunch of new features for athletes & outdoor enthusiasts under construction that will release in the near future.

Added a new section in the in-app Guide explaining how the app schedules notifications. Improved UI edge case behavior on small screen devices with max size dynamic type enabled (Accessibility). A few other small enhancements around the app. We have some big features for athletes & outdoor enthusiasts coming soon, thank you for using Swelter!

Updated the App Store listing and refined descriptions.

Several small stability enhancements and improvements.

Minor improvements.

Continued work on background and first launch app stability. Other bug fixes & enhancements. We continue to run our validation scripts comparing Swelter's algorithm against Japan's network of physical WBGT sensors. We are up to 15,059 station hours compared now; maintaining the same accuracy numbers (app's Sources & Algorithm screen updates as we run validation scripts weekly).

Improved the Guide, Sources & Algorithm screen (in Settings > About) and improved wording throughout the app. Fixed a bug so widgets now match the app exactly during a few edge cases (storms, freezing weather, and high humidity).

Improvements to first launch stability.

Fixed an issue where the app could open showing an earlier hour instead of the current one. Small UI enhancements around the app.