Wind Chill? or Actual? There's a big difference, because your chickens SHOULD NOT be drafty on their roosts. According to NOAA -23 is the coldest (actual) forecast tonight. In Rhinelander. Wind Chills will be -30 or lower in a big swath of the state.It is suppose to be negative 30 and i dont have supplemental hesting for my 3 chickens will they be okay.
And assuming they are fully feathered, adult sized birds not of one of the cold-brittle breeds (Serama's get mentioned a lot in this category) in a dry, draft free, well ventilated coop, they should be fine. According to posters raising their birds w/o heat in Canada, Alaska, North Dakota, etc.
I don't know from personal experience. I would never willingly live in a place that went below 0 routinely or protractedly. I hate getting dressed.