The conversion

85°F = 29.44°C

°C = (°F − 32) × 5/9, so (85 − 32) × 5/9 = 29.44.

As an outdoor air temperature, 85 °F sits in the warm 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 85 °F.
FahrenheitCelsius
80 °F26.67 °C
81 °F27.22 °C
82 °F27.78 °C
83 °F28.33 °C
84 °F28.89 °C
85 °F29.44 °C
86 °F30 °C
87 °F30.56 °C
88 °F31.11 °C
89 °F31.67 °C
90 °F32.22 °C

The other direction

29.44 °C converts back to 85 °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.