The conversion

140°F = 60°C

°C = (°F − 32) × 5/9, so (140 − 32) × 5/9 = 60.

As an outdoor air temperature, 140 °F sits in the hot 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 140 °F.
FahrenheitCelsius
135 °F57.22 °C
136 °F57.78 °C
137 °F58.33 °C
138 °F58.89 °C
139 °F59.44 °C
140 °F60 °C
141 °F60.56 °C
142 °F61.11 °C
143 °F61.67 °C
144 °F62.22 °C
145 °F62.78 °C

The other direction

60 °C converts back to 140 °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.