While most settings on the iPhone can be found in the Settings app, one that is missing seems to be a way to change the display of temperature in the Weather app from Fahrenheit to Celsius or Celsius to Fahrenheit.

Here is how to change the units setting for temperature in iOS 5. Other versions might be slightly different:

  1. Open the Weather app that came with your iPhone.
  2. Tap on the lowercase “i” icon in a white circle which can usually be found at the bottom right of the screen.
  3. Touch the °C or °F unit of measure that you prefer for displaying weather temperature at the bottom of the screen.
  4. Click the Done button at the top right of the screen to exit the weather settings.

The next time you open your Weather app, the weather should appear correctly. Note that this change can affect other weather apps as well.