Did you know that the sky is blue today for the same reason the sunset was orange on Wednesday? As mentioned by a commenter in yesterday's sunset photo extravaganza post it is Rayleigh scattering that produces the clear sky colors. Lord Rayleigh, co-discoverer of argon, figured out that light gets preferentially scattered (warning: nerdy pdf with calculus) when it runs into tiny objects like the molecules of nitrogen and oxygen that make up most of the atmosphere. Shorter wavelength blue light gets scattered more than longer wavelength red and orange. During the day the scattered blue light dominates in the sky away from the sun's direct rays.

Sunlight travels a much greater distance through the atmosphere at sunset, so all the blues and greens get scattered away, leaving only the longer wavelength yellow, orange and red light. Wednesday's sunset was particularly spectacular because of the cloud placement. Very clean air to the west allowed the higher level clouds to be bathed in the orange light.

Woo-hoo! Yesterday's high of 91 put 2010 in the exclusive "30 days of 90 degree weather" club! The record is 39 days shared by 1991 and 1993. The loser is 1902, when only one day got that warm.

It wouldn't surprise us if the temperature reached 90 again today. Much less humid air should pour into the region early this afternoon; giving the mercury a boost. Cool air arrives later, which means Saturday should be awesomely sunny with a high in the low 80s. Sunday will see cooler weather and a slight chance of showers in the afternoon.