Centigrade (Celsius) and Fahrenheit conversions for common meteorological temperatures :

      °C     °F

     -40    -40
     -35    -31
     -30    -22
     -25    -13
     -20     -4
     -15      5
     -10     14
      -5     23
       0     32
       5     41
      10     50
      15     59
      20     68
      25     77
      30     86
      35     95
      40    104
      45    113
      50    122