Hard Freeze This Morning

 Much of the region dropped below freezing this morning, with the main exceptions being locations close to large bodies of water.

Even my neighborhood in Seattle, not far from the water, awoke to glazed cars and icy roofs (see below).

The patterns of the frost were intricate and quite beautiful:

So how cold did it get?   The map below shows the low temperatures this morning.  Below freezing over much of western Washington, while eastern Washington was in the teens or low 20s, with a few single-digit temperatures over northeast Washington.

If you like cold, the Methow Valley did not disappoint, with most stations in the teens.

Keep in mind that the above temperatures are NOT at ground level, but at 2 meters (about 6 feet) above the surface, which is the standard height for surface air temperature.  

On cold, nearly clear nights, like last night, the ground temperatures are considerably cooler than at 6 feet.

I checked that out this morning with a research-quality thermometer over a grassy area.

Frost was evident, and the ground temperature was 29.4°F.

At 6 feet, the temperature was 33°F. An inversion (temperature increasing with height) was evident.

Tomorrow morning should be icy as well....so be careful...