Southwest Climate Outlook October 2020 - Climate Summary

Oct. 15, 2020
Ben McMahan

Monthly Precipitation and Temperature: September precipitation ranged between record driest and below average in most of Arizona and much of New Mexico (Fig. 1a). September temperatures were above average to record warmest in Arizona and average to above average in most of New Mexico (Fig. 1b). The daily average temperature anomalies for Sept. 1 – Oct. 14 (Fig. 2) highlight the fluctuations at select stations around the region.

Figure 1
Figure 2

Monsoon Precipitation: Monsoon precipitation (June-July-August-September) was record driest to much below normal (bottom 10%) across Arizona and ranged from near normal to record driest in most of New Mexico (Fig. 3) (see monsoon recap).

Figure 3

Water Supply: Water year precipitation (Oct 2019 – Sept 2020) was near normal to above normal in parts of southwestern Arizona and southern New Mexico (along with west Texas and southern California), while most of the Four Corners region, northern New Mexico, and southern Colorado were below normal or much below normal (Fig. 4). Many of the reservoirs in the region are at or below the values recorded at this time last year. Most are below their long-term average (see Arizona and New Mexico reservoir storage).

Figure 4

Drought: The Sept. 4 U.S. Drought Monitor (USDM) showed widespread areas of extreme drought (D3) and pockets of exceptional drought (D4) across Arizona and New Mexico, along with much of Nevada, Utah, and Colorado (Fig. 5). A major driver for this drought characterization was the well below average monsoon precipitation and accumulated long term precipitation deficits. The USDM from Jun. 30, 2020, highlights just how much drought expanded with the record or near-record dry monsoon across much of the southwest (Fig. 6)

Figure 6

ENSO Tracker: La Niña conditions are present and are expected to continue through winter (see ENSO tracker for details).

Precipitation and Temperature Forecast: The three-month outlook for Nov through Jan calls for increased chances for below-normal precipitation across much of the southwestern U.S. and all of northern Mexico (Fig. 7, top). The three-month temperature outlook calls for increased chances of above-normal temperatures across most of the southwestern U.S. and northern Mexico (Fig. 7, bottom).

Figure 7

Online Resources

  • Figures 1 - National Centers for Environmental Information - ncei.noaa.gov
  • Figure 2 - Climate Assessment for the Southwest - climas.arizona.edu
  • Figure 3, 4 - West Wide Drought Tracker - wrcc.dri.edu/wwdt
  • Figure 5, 6 - U.S. Drought Monitor - droughtmonitor.unl.edu
  • Figure 7 - International Research Institute for Climate and Society - iri.columbia.edu