hours per year
How it's counted. Each station has 8,760 hourly readings from a Typical Meteorological Year (TMY3, built from 1991–2005 observations; a few stations use a single recent year). An hour counts when the temperature is inside your range, it's inside the work window, and it passes the dry tests you have ticked. Every day of the week counts.
Rain. TMY files don't carry reliable rain records, so an hour is treated as rain or drizzle when the sky is fully overcast and relative humidity is 90% or higher. That catches steady rain, drizzle and fog well. It misses brief sunny-day thunderstorms, so Florida and the Gulf Coast look a little better than they really are.
The shading between dots is estimated. Colors between stations are blended from the nearest stations and fade where the closest one is more than about 400 km away. Mountains matter more than distance: a valley town and a nearby peak can differ by hundreds of hours. Trust the dots; read the shading as a rough regional picture.