Heat Watch
Unlike previous years, this June did not see extended extreme heat waves, but did see sustained warmer-than-average temperatures throughout the month and into July. Figure 11 shows the daily temperature anomalies for several Southwest U.S. cities. The histograms (on the right) show the number of days when temperatures reached levels above or below average. For example, in El Paso there were 8 days where temperatures were 6-8°F above average, and 10 occurrences where temperatures were 8°F or more above average. Although El Paso only broke the maximum temperature on one day (June 2), the city experienced 20 days over 100°F (38°C) during June—El Paso experiences about 15 days over 100°F in an average year.
Figure 11 (above): Daily temperature anomalies from June 1 – July 16, 2018 (left) and frequency of temperature anomalies (right). Figure adapted from July Southwest Climate Outlook.
Other cities along the Rio Grande broke temperature records in June and July. On June 23 and 24, Del Rio, Texas reached 106°F (41°C). Maximum temperatures in Santa Fe, New Mexico, set records on June 26 and 28 (97°F [36°C] and 98°F [36.7°C], respectively) and, although the record was not broken on June 27, the maximum temperature recorded was 100°F. Moving into July, record temperatures were set in Laredo, Texas, June 30-July 2, with temperatures of 104°F (40°C), 104°F, and 103°F (39.4°C), respectively.
In Mexico, the highest temperatures recorded in the most populated cities across Northwest Mexico were 113°F (45°C) in Mexicali on June 12, and 111.2°F (44°C) in Hermosillo and Ciudad Obregón, Sonora, on June 4 and 12, respectively. Ciudad Juárez, Chihuahua reached 105.8°F (41°C) on June 11-12, Culiacán, Sinaloa reached 104.9°F (40.5°C) on June 2, and Chihuahua, Chihuahua reached 104°F (40°C) on May 30. None of these temperatures broke previous records. Extreme temperatures for July were recorded in Sonora, with 120.2°F (49.0°C) in San Luis Rio Colorado and 119.3°F (48.5°C) in Hermosillo, both on July 5.
Looking ahead, forecasts indicate that temperatures will be above average over the next month for both New Mexico and Texas (Figure 5). A new heat forecasting tool produced by the U.S. National Weather Service provides additional insight into near future temperatures. HeatRisk is an experimental forecasting tool for visualizing heat risk potential one-week in advance (Figure 12).
Figure 12 (above): Screenshot of NWS HeatRisk for July 23. The table (right) describes the meaning of each color.
It is designed to provide guidance to decision makers and heat-sensitive populations (such as outdoor workers and those with young children) on when to take action to prepare for a heat event. Each color category shown in the map represents different levels of risk and specifies the population that is at risk. For example, yellow is a low-level of risk and means that those who are extremely sensitive to heat should take action to prevent illness. When the highest level (magenta) is forecasted, the entire population is at risk, due to long-duration heat with little to no relief overnight. HeatRisk can be accessed from the National Weather Service page for most cities (https://www.wrh.noaa.gov/wrh/heatrisk/?wfo=epz).
Extreme heat causes the most deaths in the U.S. of any weather-related disaster, according to the National Center for Environmental Information, and it is particularly important to be prepared for the unrelenting heat. Populations typically at increased risk of heat-related illness include children, pregnant women, elderly, those taking medications, those working outdoors, those with disabilities, those without adequate cooling, and the socially isolated. Be sure to check on loved ones and neighbors and call 911 if anyone is experiencing symptoms of heat stroke (e.g., headache, fast pulse, confusion, nausea, loss of consciousness). For more information on vulnerable populations, the symptoms of heat-related illness, and what to do to prepare, visit the CDC extreme heat webpage (en Espanol: https://www.cdc.gov/es/disasters/extremeheat/index.html).