Why two temperature scales exist
Fahrenheit, devised by German physicist Daniel Fahrenheit in the early 18th century, predates Celsius. Celsius, based on the more intuitive reference points of water's freezing and boiling temperatures, was later devised by Swedish astronomer Anders Celsius and went on to be adopted by most of the world.
Why Fahrenheit is still used in the United States
The United States is one of the few countries that, even as the rest of the world largely shifted to the metric system, has continued using Fahrenheit -- along with other customary units -- in everyday life. Weather reports and recipes are two of the most common places it still shows up.
Frequently Asked Questions
What if a weather forecast while traveling abroad is shown in an unfamiliar scale?
The quick-estimate trick (subtract 30 from the Fahrenheit figure, then divide by 2) gives a fast approximate Celsius reading. If you need a precise number, use the full formula or a conversion app.
What if a recipe lists an oven temperature in a scale I am not used to?
Oven temperatures convert precisely using the standard formula. If you cook from foreign recipes often, keeping a small conversion chart for commonly used temperatures on hand saves you from recalculating every time.