The conversion

56°F = 13.33°C

°C = (°F − 32) × 5/9, so (56 − 32) × 5/9 = 13.33.

As an outdoor air temperature, 56 °F sits in the cool band. The other scale is on the dial beside it in the app, so a reading like this needs no conversion at all.

Convert something else

68°F

The range either side

Neighbouring values, for when the number you actually wanted was a degree or two away.

Fahrenheit to Celsius either side of 56 °F.
FahrenheitCelsius
51 °F10.56 °C
52 °F11.11 °C
53 °F11.67 °C
54 °F12.22 °C
55 °F12.78 °C
56 °F13.33 °C
57 °F13.89 °C
58 °F14.44 °C
59 °F15 °C
60 °F15.56 °C
61 °F16.11 °C

The other direction

13.33 °C converts back to 56 °F, which is the same relationship read the other way. Going from Celsius to Fahrenheit, multiply by 9/5 first and then add 32. Adding first is the usual mistake.

The full converter handles any value, in either direction, including kelvin, and shows the formula as it works.