A transition to a fall circulation pattern in the North Pacific brought generally cooler than anticipated temperatures to the west. While portions of California and Nevada saw conditions slightly above normal (0-2°F), the PNW and the desert SW experienced near normal to cooler than normal temperatures during the month (Figure 1). September precipitation amounts were mixed over the western US with the bulk of California, Oregon, and eastern Washington much drier than normal (Figure 1). However, portions of southern California and desert SW experienced monsoon flow that carried northward producing areas of 200% above normal rainfall in the intermountain west and the northern Rockies. Nationwide, precipitation patterns were mixed with the wettest areas being the northern Rockies, the upper Mississippi Valley where extreme flooding occurred, and Florida to the mid-Atlantic region due to tropical storm moisture. The rest of the southern states and up into New England saw less than 25% of normal precipitation for the month of September (not shown). September nationwide saw temperatures flip from a relatively cool pattern in the west to much above normal temperatures from the Rocky Mountain states over the whole of the eastern US. Temperatures throughout the east were 2-5°F above normal with the most astonishing record being New Orleans where they recorded a record 43 days where the nighttime temperatures did not drop below 80°F (not shown).

View Fall 2016 – October 3, 2016(PDF) >