-30°F is warmer than -30°C.
The -ve sign is used when the temperature drops down. Celsius is the greater unit. By converting, -30°F = -1.11°C (approx.) We know that, -1.11 > -30. So, -30°F (-1.11°C) is warmer than -30°C.
Formula :-
(x°C × 9/5) + 32 = y°F
_____
Hope it helps ⚜