The study uses relative humidity, which is affected by the dew point. While straight humidity is often consistent at least in the US, relative humidity fluctu

The study uses relative humidity, which is affected by the dew point. While straight humidity is often consistent at least in the US, relative humidity fluctuates wildly. Relative humidity is what gives the muginess feel. Most of the US except the Rockies and most of the West Coast have way higher relative humidity in the summer months. NYC can get especially bad (or good in this case). In the South, that increase has already started. Admittedly, it's not a huge affect, but taking your NYC example, the temperature alone will decrease the R0 by at least .5. I'll take that.