Most of the nation experience Code Green (Good) levels of PM 2.5 today, but there were some areas that experience a relatively large amount of pollution. There were Code Orange and Code Red (Unsafe for Sensitive Groups and Unsafe, respectively) levels in Idaho and Montana (AirNow, top left), and Code Purple (Very Unhealthy) levels on the border between California and Nevada. The sources of both areas of high levels of PM 2.5 are unknown. NRL's sulfate map, top right, shows that there were not high levels of sulfate in these areas. There was sulfate recorded over California, but it does not seem to be close enough to the areas with high PM 2.5 to have made a large difference. There was not smoke seen in these areas either, but the smoke seen discussed in yesterday's post from Florida seems to have stayed in the general Southeast area (NOAA, bottom left). The smoke was not caught in NASA's satellite images, most likely because of the low density of the smoke.