How do I switch between Fahrenheit and Celsius?

For this model, the screen must be lit for any button press to be effective

This feature is selected from the menu. Temperature scale is menu item #1

TO ACCESS THE SETUP MENU: 

1. Move the System Mode switch into the OFF position 
2. then hold down the SET button for approximately 5 seconds until the screen changes. 
3. The menu will always start with item #01, and is advanced to each following item by a single press of the NEXT button. 
4. The options for each item are changed using the UP or DOWN buttons.

ITEM #01 (TEMPERATURE SCALE):

[1] (default) Shows all temperature values in Fahrenheit.

[2] Shows all temperature values in Celsius

 Use up down button to select desired scale. Move slide switch to exit or wait for it to time out or press next until end of menu is reached