Late May weather trends:  No letup with steam heat, wind, and no rainfall (click to enlarge)
No Letup in Sweltering Heat as May Ends
Heat, Fire, Other Dangers Continue as no more Rain Falls

The Situation
Update: If you thought most of April was impressively hot, then most of the last ten days of May will actually feel even hotter in many areas. The combination of a flat upper level high pressure ridge and a continued fast storm track across the northern half of the U.S. has led to persistent and frequently strong southerly flow across Deep South Texas. Additional atmospheric drying is expected to close the month, due to subsiding (sinking) air around the atmospheric high pressure system. This ensures no rain for the region through the 31st; perhaps into early June. The early month respite from heat and humidity, followed by a five day period which featured some rainfall, was just a memory as of May 18th. The return of heat along with paltry long term rainfall trends – and, for those near the Rio Grande beteen McAllen and Falcon Heights (at the south end of Falcon Lake), virtually no rainfall since October, exceptional drought and extreme wildfire growth potential continues. The animated map below shows the national trend of weather systems through May 31st.

The first half of May included a few fronts and even some severe weather, which held temperatures in check – near or just below long term averages. The return to the windy, hot, and humid conditions that dominated much of April brought temperatures back to 2 to 3°F above average, and by month’s end, these values will top out between 3 and 4°F above average, ranking May 2011 in the top portion of all time temperatures. A summary will be available on June 1st.

Stay a Number of Ways

  • Heat Safety:
    • Drink Plenty of Water, even if you’re not thirsty.
    • Take Frequent Breaks if working outdoors. Save strenuous work or excercise for the early morning or late evening
    • Wear lightweight, light colored, and loose fitting clothing.
    • Heat sensitive persons should remain in air conditioned buildings if at all possible
    • Wear sunscreen and a hat to protect from extreme ultraviolet rays, which are peaking
    • Beat the heat, check the backseat! Ensure that young children and pets are taken out of vehicles
  • Fire Weather Safety:
    • Continue to cut grass and brush to very low heights, including areas where last week’s rains may have sprouted new growth
    • Refrain from using welding or grinding equipment in high grass or brush
    • Park vehicles on dirt or paved areas; hot catalytic converters often produce sparks which can quickly ignite a rapidly growing grass or brush fire.
    • Use vehicle ash trays to dispose of cigarette butts.
    • Burn bans remain in effect for most of the Rio Grande Valley. Check with local authorities for additional details.
  • Rip Current Safety:
    A moderate to high risk for rip currents is expected for most days through the rest of May. Poor swimmers should remain in water no higher than knee deep, and even experienced swimmers should venture into the surf no higher than waist deep. Currents are highest around the Boca Chica/Isla Blanca jetties (Isla Blanca Park) and at the public beach access points from Andy Bowie Park northward. Beat the heat very cautiously if entering the surf through the end of May.


For much more on these and other hazards, check out our Preparedness Page.

Late May weather pattern across the United States, 2011
Above: Expected atmospheric and surface weather patterns, on May 28th and May 31st. White curves indicate mid level, or "storm track", flow. Storm system motion from the Central Plains through the Ohio Valley to start the period will shift much farther north by the end of the month, with a large, warm, and dry upper ridge covering the eastern half of the country. This ridge will end the severe weather that has plagued the Mississippi and Ohio Valleys, and deepening easterly flow may bring azure blue skies to the Valley to begin June. is the U.S. government's official web portal to all federal, state and local government web resources and services.