CLIMAS and Arizona Cooperative Extension will host an online climate briefing about the 2009 monsoon for natural resource managers, extension faculty, and interested citizens on May 21 at 10:00 a.m. PDT. Colleagues from northern Mexico are especially invited to participate, as forecasts will cover the U.S.-Mexico border region.
Trends in the frequency of precipitation events in which precipitation over a 7-day duration exceeds a 1-year recurrence interval for each particular climate division. Blue circles are positive trends, red circles are negative trends. The magnitude of the trend is linearly proportional to the radius of the circle.
The map shows the mean calendar date of monsoon onset, based on the time frame 1963–1988. Onset definitions vary depending on region because of differences in rainfall regimes. Although average onset date may change slightly if different time frames are used, the relative timing of the northward progression of the monsoon should remain intact.