A strong upper-level subtropical ridge/heat dome centered over central and southern Mexico strengthened and shifted northward towards the Rio Grande Valley and Deep South Texas ranchlands the week prior to Memorial Day. The strong ridge aided lower level temperatures at around five thousand feet to soar to between 78 and 86F, which translated to surface temperatures rising into the upper 90s to…
Every event with a place to put it; 32 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS BRO wrote it up.
A strong upper-level subtropical ridge/heat dome centered over central and southern Mexico strengthened and shifted northward towards the Rio Grande Valley and Deep South Texas ranchlands the week prior to Memorial Day. The strong ridge aided lower level temperatures at around five thousand feet to soar to between 78 and 86F, which translated to surface temperatures rising into the upper 90s to mid 100s on most days between May 21-25. With dewpoint temperatures well into the 70s to around 80, apparent temperatures (feels like temperatures) ranged anywhere between 111-116F across parts of Deep South Texas and the Rio Grande Valley with a few locales reaching higher than this. The hottest apparent temperatures were located along and east of IH-69C from Hidalgo and Brooks County to Cameron, Willacy, and Kenedy County - but all of Deep South Texas observed at least dangerous heat levels by local definition (111F or higher for at least two hours) on most days.
Actual temperatures during the period were even hotter than the peak of the summer heat (late July through mid August) for most areas. The month would shatter all-time temperature records by 1 to more than 3 degrees.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Brownsville, TX wrote its last area forecast discussion before the first event at May 21, 11:33 AM CST, 20 minutes earlier.
Area Forecast Discussion...UPDATED National Weather Service Brownsville TX 1233 PM CDT Tue May 21 2024 ...New AVIATION... .SHORT TERM... (Today through Wednesday) Issued at 304 AM CDT Tue May 21 2024 594dm Subtropical Ridge anchored over N Mexico and South Texas to maintain the above seasonal heat and keep our region rain free today through Wednesday. 850mb temperatures of 22-24C, dew points in the upper 70s to upper 60s support heat indices in the 110-115 range for all areas with except to the coast and Island counties. A heat advisory will be issued from 1-6 PM to cover the dangerous heat today. Another heat advisory is possible Wednesday with no substantial change to the airmass or the position of strength of the 500mb ridge. No relief overnight with minimums also remaining above normal with mid 70s to 80 degrees as low as they go with a modest southeast breeze and some increasing overnight cloudiness keep any radiational cooling at a minimum or zero. Otherwise, morning lower clouds break up fairly quickly each mid to late morning with plenty of afternoon and early evening Sun along with some afternoon gustiness. Also, hazy skies persist with agricultural fires from southeast Mexico continue to spread north with the southeasterly flow. Local air quality will be impacted with AQI in the 'Unhealthy for Sensitive groups" forecast for the RGV including the lower coast today and Wednesday. && .LONG TERM... (Wednesday Night through Monday) Issued at 304 AM CDT Tue May 21 2024 Building heat will be the main concern during this portion of the total forecast. The BRO CWFA will remain on the northern periphery of 500 mb high pressure centered over Mexico, resulting in well above normal daytime high and overnight low temperatures. A HEAT ADVISORY is a near certainty daily beginning on Thursday, and an EXCESSIVE HEAT WARNING cannot be ruled out entirely beginning on Friday, with areal coverage of the WARNING likely being the key factor each day as to whether or not it is issued. Additionally, the presence of the 500 mb high will result in dry weather, with no precipitation anticipated. However, beyond the end of the Long Term period, on Tuesday night and Wednesday, some model guidance suggests that the passage of a mid-level shortwave may generate a wave of strong to severe thunderstorms through Deep South Texas and the Rio Grande Valley with welcome/needed rainfall at that time. && .AVIATION... (18Z TAFS) Issued at 1228 PM CDT Tue May 21 2024 Mostly MVFR conditions are expected to occur off and on during the TAF cycle at all TAF sites. VFR conditions are expected to last through the afternoon and into the evening hours before giving away to mostly MVFR. Southeasterly winds are expected to hold through the period while being gusty during the afternoon. The winds are expected to weaken during the evening hours and remain light through the overnight hours before picking back up again late in the morning again tomorrow. && .MARINE... (Today through Wednesday) Issued at 304 AM CDT Tue May 21 2024 A moderate pressure gradient persist over the Lower Texas coastal as a high pressure ridge extends from Florida to the SW Gulf of Mexico. Moderate to locally fresh southeast winds and slight to moderate seas can be expected today through Wednesday. (Wednesday Night through Monday) High pressure over the Gulf of Mexico will interact with thermal low pressure over Mexico to produce an enhanced pressure gradient along the Lower Texas Coast through the period. Small Craft Should Exercise Caution and/or Small Craft Advisory is likely to be needed daily to account for the breezy winds and elevated seas. && .PRELIMINARY POINT TEMPS/POPS... BROWNSVILLE 97 81 96 81 / 0 0 0 0 HARLINGEN 97 77 98 78 / 0 0 0 0 MCALLEN 101 80 101 80 / 0 0 0 0 RIO GRANDE CITY 103 79 104 78 / 0 0 0 0 SOUTH PADRE ISLAND 87 82 86 81 / 0 0 0 0 BAYVIEW/PORT ISABEL 94 79 94 79 / 0 0 0 0 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...Heat Advisory until 6 PM CDT this evening for TXZ248>255-353. GM...None. && SHORT TERM...59-GB LONG TERM....66-Tomaselli AVIATION...64-Katz
The national radar mosaic for the moment the first event began.
30 heat, 2 excessive heat. Local standard time, as filed.
Brownsville/South Padre Island International Airport (KBRO) recorded max heat indices between 111 to nearly 116F for a couple of hours from 1:55-3:55 PM CDT on May 21, 2024. Harlingen Valley International Airport (KHRL) recorded max heat indices between 111F and nearly 114F from 12:53 to around 4 PM CDT on May 21, 2024.
By proxy, between locations in northern Kenedy and in northern Cameron County, Willacy County is assumed to have observed heat index values between 111 and 114F between 1 and 430 PM CDT.
The South Texas International Airport Automated Weather Observation System site, 11 miles north of Edinburg, recorded max heat indices between 111-114 from 115 through 445 PM. A Remote Automated Weather Station near Linn-San Manuel recorded max heat indices between 111-118F for 5 hours from 12:46-5:46 PM CDT - however, the site is known to run higher on temperature than surrounding locations, so the higher values (116 and more, between 146 and 446 PM CDT) are likely unrepresentative.
The Texas Mesonet site in Sarita recorded heat index values between 111F and 113F for a few hours, between 150 and 320 PM CDT.
Rancho Los Comitos (Texas Mesonet) recorded max heat indices of 111F for a couple of hours from 2:55-4:55 PM CDT on May 21, 2024. La Puerta Remote Automated Weather Station, 5.645 miles east of Rio Grande City, recorded max heat indices between 112-120F for 6 hours from 12:11-6:11 PM CDT on May 21, 2024. However, the site is known to be unrepresentative compared with proxy observations, so the higher values (116 and above) were not used for this event. Time was adjusted by proxy to add an hour on either side of the Rancho Los Comitas location.
Zapata recorded max heat indices between 111-113F for a little more than four hours from 215 through 625 PM CDT on May 21, 2024.
McAllen International Airport (KMFE) recorded max heat indices between 111-117F for 6 hours from 11:53 AM-5:53 PM CDT on May 21, 2024. A period of excessive heat - 116F or higher - lasted from 230 PM to 430 PM CDT.
Rancho Los Comitos (Texas Mesonet) recorded max heat indices of 111F for a couple of hours from 2:55-4:55 PM CDT on May 21, 2024. By proxy, it can be interpolated to southern Jim Hogg County to have similar values at a similar time. Hebbronville, in northern Jim Hogg County, touched 111F at 350 PM.
Falfurrias (AWOS) recorded max heat indices of an estimated 111 or higher for a few hours during the afternoon. Actual observations were much higher, but not matched by nearby proxy observations which did not show values at or above 116F, which is the baseline for Excessive Heat events (lasting 2 or more hours) between 3:55-5:55 PM CDT.
McAllen International Airport (KMFE) recorded max heat indices between 111 and just below 116F for 5.5 hours from around 1230 through 6 PM CDT on May 22, 2024. Weslaco, farther east, touched 111 at 255 PM CDT, but South Texas International Airport 11 miles north of Edinburg and along the south/north Hidalgo line reached 112 to 114F+ generally between 155 and 555 PM CDT.
Brownsville/South Padre Island International Airport (KBRO) recorded max heat indices between 111-114.5F for a little more than 3 hours from 1:53-5:30 PM CDT on May 22, 2024. Harlingen Valley International Airport (KHRL) recorded max heat indices between 111-114F for nearly four hours from 130 to 515 PM CDT on May 22, 2024.
Harlingen Valley International Airport (KHRL) recorded max heat indices between 111-114F for nearly four hours from 130 to 515 PM CDT on May 22, 2024. By proxy, and data from northern Kenedy (1 hour of 111 to 112 heat index during this window), it can be inferred that inland Willacy County had similar heat index values for a similar period of time.
The South Texas International Airport 11 miles north of Edinburg recorded max heat indices between 111 and 114.5F between 155 and 515 PM. The Linn-San Manuel Remote Automated Weather Station recorded max heat indices between 114-116F degrees for a couple of hours, between 1:46-3:46 PM CDT on May 22, 2024 - but these values were likely too high based on proxy observations, which were close to what was observed elsewhere nearby.
McAllen International Airport (KMFE) recorded max heat indices between 111 and just below 116F for 5.5 hours from around 1230 through 6 PM CDT on May 23, 2024. Weslaco, farther east, held below 110 through the afternoon, but South Texas International Airport 11 miles north of Edinburg and along the south/north Hidalgo line reached 112F between 215 and 415 PM CDT (with a few breaks).
Brownsville/South Padre International Airport (KBRO) recorded max heat indices between 111 and just below 114.5F for around four hours from around 130 through 530 PM CDT on May 23, 2024. Harlingen/Valley International Airport (KHRL) stayed just below criteria due to slightly lower humidity, but the southern half of inland Cameron likely reached criteria.
Zapata recorded max heat indices between 111 and 113.5F between 335 and 655 PM CDT.
Brownsville/South Padre Island International Airport (KBRO) recorded max heat indices between 111-115F for 5 hours, from 11:43 AM to around 5:00 PM CDT. Harlingen Valley International Airport (KHRL) recorded max heat indices between 112-115F for 3 hours, from 12:52-3:52 PM CDT on May 24, 2024.
The Mesonet site at Sarita in northern Kenedy County observed heat index values between 111 and 114 from 1230 until 530 PM.
Harlingen Valley International Airport (KHRL) recorded max heat indices between 112-115F for 3 hours, from 12:52-3:52 PM CDT on May 24, 2024. The Texas Mesonet station at Sarita recorded heat indices between 111 and 114 from 1230 until 530 PM CDT. By proxy between these locations, similar values and times are assumed for Willacy County.
McAllen International Airport (KMFE) recorded max heat indices between 113-121F for 5 hours, from 11:53 to around 6:30 PM CDT on May 24, 2024. Heat indices reached Excessive Heat Warning criteria with values between 116-121F for 4 hours, from around 130 until 530 PM. At South Texas International Airport 11 miles north of Edinburg and on the line between north and south Hidalgo County, peak heat index ranged from 112F to 117F between around 125 and 615 PM CDT, peaking qt 117F between 315 and 415 PM. Weslaco Mid-Valley airport, in southeast Hidalgo, reached 111 to near 113F between 230 and 400 PM.
Falfurrias (AWOS) recorded max heat indices between 111-118F for 6 hours, from 12:55-6:55 PM CDT on May 24, 2024. Though excessive heat values between 116-118F occurred for a couple of hours, between 3:55-5:55 PM CDT, proxy/trusted locations in northern Hidalgo County and inland Kenedy County suggest that the Brooks Co Airport site may have only briefly touched 116F, the starting point for Excessive Heat.
At South Texas International Airport 11 miles north of Edinburg and on the line between north and south Hidalgo County, peak heat index ranged from 112F to 117F between around 125 and 615 PM CDT, peaking qt 117F between 315 and 415 PM. The Remote Automated Observing Station at Linn-San Manuel recorded max heat indices between 114-120F degrees for 5 hours, between 12:46-5:46 PM CDT on May 24, 2024.
Though heat indices reached Excessive Heat Warning criteria (116 or higher for two or more hours) at Linn/San Manuel with values between 118-120F for 3 hours, from 2:46-5:46 PM CDT, the site has a known high bias and proxy values were more likely close to 116F or 117F for about an hour.
Zapata recorded max heat indices between 112-114F from 1:55-7:55 PM CDT on May 24, 2024.
Rancho Los Comitos in northern Starr County (Texas Mesonet) recorded max heat indices between 111-115F for 4 hours, from 3:00-7:00 PM CDT on May 24, 2024. La Puerta - 5.65 miles east of Rio Grande City (Remote Automated Weather Station) recorded heat indices between 112-123F for 7 hours, from 12:11-7:11 PM CDT on May 24, 2024. Though Heat indices reached Excessive Heat Warning with values between 120-123F for 4 hours, from 2:11-6:11 PM CDT, these values are notoriously high and therefore not considered representative of the county as a whole. Therefore, an hour has been added to the start and end time based on the Mesonet site.
Hebbronville recorded max heat indices between 111-113F from 2:50-6:50 PM CDT on May 24, 2024.
McAllen International Airport (KMFE) recorded max heat indices between 111-118F for 6 hours, from 11:30 AM-615 PM CDT on May 25, 2024. Peak value reached just below 118 at 353 PM, with values likely at 116 or higher from 330 and 430 PM. South Texas International Airport (11 miles north of Edinburg) recorded max heat indices of 112F for 4 hours, from 11:15 AM -5:55 PM CDT on May 25, 2024.
South Texas International Airport (11 miles north of Edinburg) recorded max heat indices of 112F for 4 hours, from 11:15 AM -5:55 PM CDT on May 25, 2024.The Remote Automated Weather Station at Linn-San Manuel recorded max heat indices between 112-117F degrees for 7 hours, between 10:46 AM-5:46 PM CDT on May 25, 2024. However, this location is notoriously high, so it is more likely that proxy heat index values were closer to 111 to 114 and the duration was similar to that of the South Texas International Airport.
Brownsville/South Padre Island International Airport (KBRO) recorded max heat indices between 111-113F for a couple of hours, from around 11:30 through around 3 PM CDT on May 25, 2024. Harlingen Valley International Airport (KHRL) recorded max heat indices between 111-115F for from around 1230 until 330 PM CDT.
Harlingen Valley International Airport (KHRL) recorded max heat indices between 111-115F for from around 1230 until 330 PM CDT. By proxy, it is inferred that at least southern Willacy County experienced similar conditions to northern Cameron (near Harlingen).
Zapata recorded max heat indices between 111-116F for 5 hours, from 12:55-5:55 PM CDT on May 25, 2024.
The Texas Mesonet site at Rancho Las Comitas reached 111 to 114 heat index values from 225 until 330 PM. La Puerta (Remote Automated Observing Station) recorded max heat indices between 114-119F for 6 hours, from 12:11-6:11 PM CDT on May 25, 2024. Heat indices reached Excessive Heat Warning criteria with values between 117-119F for 4 hours, from 1:11-5:11 PM CDT. However, the location, 5.65 miles east of Rio Grande City, has a known high bias. Proxy values from Rancho Las Comitas were used, with an hour of duration added on each side of the period for a better estimate.
Falfurrias (AWOS) recorded max heat indices between 111-118F for 7 hours, from 11:55 AM-6:55 PM CDT on May 24, 2024. However, the location was likely having sensor issues for the latter half of May, as their observations were not commensurate with nearby sites as proxies. Therefore, the best estimate for Brooks County was closer to 111 to 114 from 3 until 6 PM CDT.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Texas in 2024Every state in 2024This day in weather historyWarnings in Texas, May 2024
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1180529, 1184133, 1180538, 1184132, 1180637, 1182540, 1188904, 1188909, 1180643, 1182588, 1182583, 1184135, 1182590, 1188952, 1188960, 1188941, 1182635, 1184138, 1184139, 1189054, 1182698, 1182659, 1182670, 1182669, 1182699, 1183028, 1183027, 1183031, 1184141, 1182702, 1182708, 1182700.