Here is a photo of a lilac bush with frost only on one part!, Cold Temperatures is was caused this, Here is what happened, We have a wood burning stove, and with the cold temperatures last night around -16.F and clear skies, The smoke coming out of the wood burning stove was warm and moist, this caused frost only to form where the smoke came in contact with the branch's!!!

Highs today were warmer across the area, with high temperatures between -3.F and 1.F here is a list of HIGH temperatures Sunday
Spooner,WI -3.F
Amery,WI 1.F
New Richmond,WI -0.F
Clayton,WI 0.F
Rice Lake,WI -0.F