Regional Climate Overview - July 2017 - September 2017
Over the last three months (July – September) precipitation was 25–90% below average for areas in western and southern New Mexico and Texas (Figure 1; left). Northeast New Mexico, North Texas, and small areas along the southern Rio Grande experience precipitation 150–300% above average. Temperatures were above average (0–2 °F; 0–1.1 °C) for most of the Rio Grande Basin over the same time period (Figure 1; right).
Figure 1 (above): Percent of average precipitation (left) and departure from average temperature in degrees F (right), compared to the 1981–2010 average, for 7/1/2017–9/30/2017. Maps from HPRCC.
July to September was cooler than normal in Sonora and the Chihuahua-Coahuila border, which broke the trend of warmer-than-average temperatures for this summer. Temperatures were warmer than normal in southern Chihuahua and portions of Northeast Mexico where anomalies were greater than 5°C (9°F) (Figure 2, left). Sonora and portions of the Northeast accumulated the greatest number of days above 40 °C (104 °F); more than 45 days in Sonora and more than 30 in the Northeast (Figure 2, right).
Figure 2 (above): Temperature anomalies in °C (left) and number of days with maximum temperatures at or above 40 °C (104 °F) (right) for July–September. Maps from SMN.
Temperatures from October 1–16 were 0–6 °F (0–3.3 °C) above average for almost all of New Mexico and Texas (figure not shown). Precipitation over the same time period was 0–75% below average for most of Texas and West and Southeast New Mexico. Exceptions were eastern and southern New Mexico, and North and South Texas, where precipitation was 200–800% above average. For the first nine months of the year (January – September) minimum temperatures have been the warmest on record for New Mexico and the second warmest for Texas (NOAA). Minimum temperatures, usually measured just before sunrise, are important, especially during the hot summer months, because high minimum temperatures reduce the opportunities for people—especially those without air conditioning—to recover, overnight, from prolonged exposure to high temperatures.
Abnormally dry conditions have returned to western New Mexico over the past month, according to the North American Drought Monitor (NADM) (Figure 3). Drought conditions were eliminated near Del Rio and in Coahuila, but have worsened in Tamaulipas, Nuevo León, and southern Texas where abnormally dry and moderate drought conditions have persisted and expanded. Drought development is likely in western and southern Texas by January, according to the U.S. Seasonal Drought Outlook.