No relief in sight for oppressive early May heat across the Rio Grande Valley, May 4-8, 2009
The Heat is On!
Heat, Drought Increasing Stress on Humans, Animals, Plants
No relief through Mid May

Heat, heat stress, drought, and continuing longshore and some rip currents will continue unabated through the middle of May. Under abundant sunshine most of the time, daytime temperatures will continue to reach or exceed to century mark, or 100°F, across the western two thirds of the Rio Grande Valley and Deep South Texas, and reach 95 or higher elsewhere, except toward the immediate coast, where relative ‘cooling’ Gulf breezes will hold temperatures down a bit. Area wide, temperatures will run about 10 degrees above seasonal averages, which are in the mid 80s to lower 90s. Breezy to locally windy conditions will return by May 5th, and continue periodically into the weekend of May 9th and 10th. The combination of hot temperatures, May sunshine, and occasionally strong winds will continue to intensify the current drought.

Heat Stress
The combination of heat and humidity will make it feel more like 105°F to 110°F each afternoon across most of the area. These conditions are more indicative of mid July than mid May. While residents are quickly acclimating to an early summer, the combination of its early arrival with a larger than normal number of people expected to be outdoors due to a number of school closures due to the threat of the H1N1 influenza virus, increases the potential for heat health related incidents. Persons expected to spend any length of time outdoors for the next week are urged to follow these safety tips:

  • Slow Down. Schedule strenuous activities early in the morning, if at all.
  • Drink Plenty of Water. For healthy persons, be sure to drink water at all times, even if you are not thirsty. Persons on fluid restricting diets should consult their physicians before increasing consumption.
  • Dress for Summer. Lightweight, light colored clothing reflects heat and sunlight and helps maintain a lower body temperature.
  • Do not Drink Alcohol. Alcoholic beverages increase dehydration rate and could bring on heat stress or heat stroke rapidly.
  • Spend time in Air Conditioning. Cooler locations offer relief and some protection from heat dangers.
  • Avoid Sunburns. Sunburn makes heat dissipation from the body more difficult.
  • Never Leave Children Unattended in Vehicles. Not even for a minute! Temperatures rise rapidly inside a car, nearly 30°F in as little as 20 minutes. Click here for more information on children and hyperthermia.
For much more information, go to the National Weather Service's Heat Safety web page.


Wildfire Growth Potential
Though surface dew points will increase a little through the week, some of the increase may be countered by higher air temperatures, allowing afternoon relative humidity to remain marginal or even fall below critical thresholds, when combined with continuing drought stressed grasslands and other fuels. Winds increasing to 20 mph or higher from May 5th through at least May 7th will increase the threat for rapid wild fire growth. Burn bans remain in effect for most counties in Deep South Texas and all of the Rio Grande Valley. Continue to monitor this web site for updates on fire weather conditions through the week, including Fire Danger statements and possible Fire Weather Watches and Red Flag Warnings.

Longshore and Rip Currents
Waves, seas, and swell will be generally lower this week than they were from April 26th through May 2nd. However, the combination of the heat with school cancellations may increase the number of beach goers. Longshore and rip current potential will pick up by May 5th and continue through the week, reaching a high risk from time to time. As surf temperatures warm toward 80°F, more local residents will want to seek relief from the heat in the water. Inexperienced swimmers should continue to use caution when venturing into the water. Experienced swimmers and surfers should remain alert to the current and be ready to take evasive action if needed. Remember, alcohol and longshore/rip currents can be a deadly mix.

Weather wise, the upcoming week will feature a stable pattern of a flat upper level ridge extending from the Pacific Ocean west of southern California east southeast through Arizona, New Mexico, and much of Texas. Farther north and east, a broad, somewhat flat upper level trough will bring occasional rains and somewhat below seasonal temperatures from the Upper Midwest through the Mid Atlantic and Northeast U.S. (map, below). This pattern will maintain a continuation of south to southeast surface flow, and south to southwest flow above the surface, keeping unseasonably hot temperatures in place while subsiding air associated with the ridge holds dry air throughout the depth of the atmosphere and leaves rain chances close to nil.

500 millibar (close to 18 thousand feet) weather features contributing to the continuing heat wave, first half of May, 2009
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