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Fig. 1: A rainfall index (average statewide departure from normal of rainfall) for JUL-SEP during wet monsoon years from 1996-2020.  

Discussion: The Climate Impact Company month 1-3 ahead forecast indicated increasing risk of a wet monsoon beginning in July and centered mostly on Arizona and New Mexico. Looking at wet monsoon JUL-SEP period(s) since 1996 for the Great Basin and Southwest States identifies 8 years when wetter than normal conditions were present across at least 2 of the 4 states (Fig. 1). The consensus of the 8 years depicts wet conditions over the Southwest U.S. with correlating dry climate in the Upper Midwest/Midwest U.S. (Fig. 2). A wet monsoon during mid-to-late summer increases the risk of a dry climate in the Upper Midwest/Midwest States where major crop areas are located. Note that the East and northwest Gulf States are wet.

Fig. 2: An analog for JUL-SEP when wet monsoon was present and precipitation patterns elsewhere across the U.S. for that time frame.