It's not too uncommon for forecasters to be 20 degrees off in their low temp predictions for Ely.
Case in point: The National Weather Service and the rest of the forecasting crews predicted a low of -6 to -8 degrees Fahrenheit last night. We woke up to a somewhat chilly 29 degrees below.
And a bit of trivia. The Celsius and Fahrenheit scales converge at 30 below. Thus, 30 below zero is the same temperature, whether measured on the Celsius or Fahrenheit scales.