It's cold..... Really cold.

[JThiessen]

You'll need to do much more than you have, and doing the whole thing (including over the intake area) will be fine. Look at a few semi's and guys with diesel pickups - they will have the entire front covered. When it warms up over xero, they will unvoer some of it.
Your intake will be able to suck air from behind the grill.

What's Nitro: When you get to temps that are below -20, and with wind, just being enclosed will likely keep the temp up about 10+ degrees than outside. And at those temps, over a certain period, fluids can and will start icing. Oils, espeically in the tranny and diffs, gets extremely stiff. Fuels start to either form frost (gasoline), and the parafin in diesel will start to solidify. The wind chill will accelerate this process. If you cant park inside, at least park with the radiator pointed away from the wind.