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# Felsius — llms.txt

## About
Felsius is a free weather app that displays Celsius and Fahrenheit side by side. It helps people who live between both temperature systems understand the weather instantly, without converting. Originally made by one person — built for expats, travellers, and mixed-unit households.

## Site
- URL: https://www.felsius.app
- App Store: https://apps.apple.com/us/app/felsius-celsius-fahrenheit/id6758587576
- Google Play: https://play.google.com/store/apps/details?id=com.felsius.app

## Content
- /learn/ – Comprehensive guide to temperature intuition and the Celsius/Fahrenheit experience
- /learn/weather-app-celsius-fahrenheit/ – Why Build a Weather App That Shows Celsius and Fahrenheit?
- /learn/why-celsius-and-fahrenheit-feel-different/ – The emotional and psychological gap between the two scales
- /learn/why-we-misjudge-temperature/ – The cognitive mechanics behind anchoring errors and unit switching
- /learn/why-fahrenheit-feels-more-precise/ – Understanding granularity vs precision in temperature measurement
- /learn/what-does-20c-feel-like/ – Calibration for 20°C (68°F), the most misread temperature
- /learn/what-is-room-temperature/ – Why "room temperature" varies by country and context
- /learn/how-hot-is-25c/ – What 25°C (77°F) feels like in sun vs shade
- /learn/how-hot-is-30c/ – Calibration for a proper summer day (86°F)
- /learn/how-cold-is-10c/ – Why 10°C (50°F) feels cooler than you expect
- /learn/why-negative-40-is-the-same/ – The one point where both scales meet
- /learn/how-hot-is-35c/ – What 35°C (95°F) actually feels like and when it becomes serious
- /learn/how-hot-is-40c/ – Extreme heat above body temperature – what changes at 40°C (104°F)
- /learn/how-cold-is-5c/ – Why damp 5°C (41°F) can feel colder than dry 0°C
- /learn/how-cold-is-0c/ – The freezing point and why 0°C days feel so different from each other
- /learn/living-between-celsius-and-fahrenheit/ – The hidden cognitive cost of switching scales daily
- /learn/why-converting-temperatures-is-mental-overhead/ – Why daily conversions accumulate into a real cognitive tax
- /learn/why-temperature-numbers-dont-map-to-comfort/ – How humidity, wind, and acclimatisation shape the real experience
- /learn/why-feels-like-temperature-makes-things-worse/ – When "feels like" temperature helps and when it just adds noise
- /learn/why-americans-struggle-with-celsius/ – Why it's not ignorance – it's how temperature intuition is built
- /learn/why-weather-apps-make-temperature-harder/ – The single-country design assumption that creates daily friction
- /learn/what-to-wear/ – Interactive guide: slide to any temperature and see what to wear, in both °C and °F

## FAQ
Q: Is Felsius really free?
A: Yes. Currently free — no subscription, no ads.

Q: Does Felsius work in my country?
A: Felsius uses weather data from national agencies worldwide including NOAA NCEP (USA), ECMWF (Europe), DWD (Germany), CMC (Canada), Météo-France, JMA (Japan), UK Met Office, Norwegian Meteorological Institute, CMA (China), BOM (Australia), KNMI (Netherlands), DMI (Denmark), ItaliaMeteo-ARPAE (Italy), and MeteoSwiss (Switzerland). If you're reading this, chances are Felsius will work for you.

Q: Does Felsius work offline?
A: Felsius needs a connection to show you the latest weather.

Q: Can I save multiple locations?
A: Yes. Up to 5 locations. Ideal for saving home, a second home, or somewhere you hope one day to be home.

Q: What does "Felsius" mean?
A: Fahrenheit and Celsius together — just like the app.

## Cite As
Felsius (https://www.felsius.app)

## Contact
hello@felsius.app