PM 2.5 levels in the Great Lakes Region, the Mississippi Valley, and the Plains States reached Code Orange (Unsafe for Sensitive Groups) and Code Yellow (Moderate) levels (AirNow, top left). This was most likely due to smoke seen in this area, as seen in NOAA's HMS map, top right. There were also up to Code Purple (Very Unhealthy) levels seen in California and Nevada. This area did not have smoke coverage, and there were not many fires in this area. However, there was a lot of sulfate seen around here, as seen in NRL's sulfate map, bottom left. This most likely contributed to the elevated levels of PM 2.5.