The continued lack of monsoon activity was reflected in persistent heat that lingered across the US Southwest for much of August and into September (Fig. 1). As mentioned last month, high pressure and sub-optimal ridge position continued to help boost daily temperatures and prevented optimal flow of moisture into the region. There have been some intermittent storm events, but little widespread storm activity that we often associate with a more typical monsoon. This lack of rain is contributing to the much warmer than normal temperatures across the Southwest, as rain events provide some relief from the summer heat. Mid-to-late August and early September both included periods of sustained record high temperatures across the region. This joins July10-13, and late July into early August, as periods where temperatures remained well above normal, including several record high temperatures (see July and Aug 2020 SWCO for details). The second week of September brought a welcome but short-lived break from these high temperatures, as numerous locations across the region swung from record highs to record lows in just a few days (Fig. 1).
- Figure 1 - CLIMAS: Climate Assessment for the Southwest - climas.arizona.edu data: RCC-ACIS