To = T*(1 + 0.2*M2)
If you know T (static air temp. in absolute units such as Kelvin or Rankine degrees), multiply it by 1.2, and that's the stagnation temperature (leading edge temp.) at Mach 1 (M=1.0).
For instance, assume T = 0 C, 273 K.
To = 328 K, or 55 C, or 131 F.