Open a weather app anywhere in the world and you will encounter one of two systems: Celsius (°C) or Fahrenheit (°F). For the vast majority of the world, Celsius is the default. For the United States, Liberia, and the Cayman Islands, Fahrenheit persists. Why? The answer is a mix of history, politics, and the extraordinary inertia of established measurement habits.

A Brief History of Temperature Scales

Fahrenheit was developed by German physicist Daniel Gabriel Fahrenheit in 1724. He set his zero point at the lowest temperature he could achieve in the laboratory — a mixture of ice, water, and ammonium chloride salt. Human body temperature was set at 96°F (later revised to 98.6°F). Water froze at 32°F and boiled at 212°F. The scale was widely adopted across Europe and its colonies throughout the 18th century.

Celsius (originally called "centigrade") was proposed by Swedish astronomer Anders Celsius in 1742. It was elegantly simple: water freezes at 0°C and boils at 100°C. This logical, base-10 structure made it naturally compatible with the metric system and far easier to use in scientific contexts. As the metric system spread across Europe from the late 18th century onward, Celsius followed.

Why Did the US Not Switch?

The United States has attempted to adopt the metric system — and therefore Celsius — multiple times. The Metric Conversion Act of 1975 made metrication a formal federal goal. The act failed to gain traction because it was voluntary, not mandatory. By contrast, European countries enacted hard metric transitions with specific dates and enforcement.

By the time the US government was seriously discussing metrication, Fahrenheit was deeply embedded in everyday American life. Building codes, cookbooks, weather broadcasts, thermostats, and decades of cultural familiarity all used Fahrenheit. The switching cost — not just economically, but psychologically and culturally — was enormous. And unlike the UK, which switched despite significant resistance, the US never applied the political will to force the change.

The Practical Difference in Weather Reporting

For weather purposes, the human-relevant range differs significantly between the two scales:

  • Celsius: most weather falls between -20°C and 45°C (a range of 65 degrees)
  • Fahrenheit: the equivalent range is -4°F to 113°F (a range of 117 degrees)

Fahrenheit's wider numerical spread means that small degree changes feel more significant — "it's dropped 10 degrees" sounds more dramatic in Fahrenheit than in Celsius, even though the actual temperature change is the same. Some argue this makes Fahrenheit more intuitive for communicating day-to-day weather variation to non-scientists.

Quick Conversion Formulas

  • Celsius to Fahrenheit: (°C × 9/5) + 32 = °F
  • Fahrenheit to Celsius: (°F − 32) × 5/9 = °C

Or use the convenient rule of thumb: double the Celsius temperature and add 30 to get an approximate Fahrenheit equivalent. (25°C × 2 = 50 + 30 = 80°F — actual answer is 77°F, close enough for casual use.)

On SunorSnow, you can switch between °C and °F instantly using the toggle in the header — all six tracked cities update simultaneously.