The Summer of 2004 through August was largely influenced by Weak Mid Latitude Westerlies, that normally retreat north for a month or two in mid to late June to August. Similar patterns like the Summer of 2004 showed up a few times in past years. From 1970 to 2004 notable summers like this, with cool fronts came in 1971, 1972, 1974, 1976, 1989, 1990, and 1992. Activity like this in August 1971 and August 1974 brought heavy rains and flooding in August. During the late summer of 1989 the weather patterns were dry. In August of 1992 several cool fronts came through the area.

The first 5 days of August 2004 began with hot afternoons, and then conditions moderated by Friday the 6th, as an early season cool front began to affect the region. One cool front on the weekend of the 7th and 8th needed the help of a series of upper level disturbances moving out of the Rockies. This brought shower activity over the area from the north and northwest. The cool front on August 11th was much stronger and brought several days of below normal temperatures the 12th, 13th and 14th. This trend extended through August 18th. This cool front was followed by a series of additional upper level disturbances aloft coming from the west, in a more September like pattern. This helped to delay return southerly winds to the area until the 17th and 18th. Several record daily lows were set. After a few days of calm weather, showers and thunderstorms returned the weekend of the 21st and 22nd, and extended into the early morning hours of Monday the 23rd. Locally heavy rains accompanied the showers and thunderstorms. At Dilley in southern Frio County, 10.51 inches of rain fell in a 12 hour period from late Sunday the 22nd to early Monday the 23rd. By late in the day of the 23rd and August 24th, a sub tropical high, typical of summer and present early in the month, began to form over the area. This allowed hot, late summer days to prevail August 25 to August 27; however by the afternoon of the 27th, the short lived sub tropical high broke down. Widely scattered showers and thunderstorms affected the western part of the area on Friday the 27th, and then dissapated in the evening. On the weekend of August 28 and 29, scattered showers and thunderstorms formed over the area. On the 30th and 31st, widely scattered shower acitvity continued. August 2004 ended cooler than normal. At Austin Bergstrom International Airport, it was the 4th coolest August of record. Most areas had below normal rainfall; however, some areas had enough locally heavy rains to make August 2004 rainfall much above normal. This was noted over parts of Frio, Dimmit, Kendall, Bandera, Edwards and Val Verde Counties. Del Rio ended up wetter than normal for August. Austin and San Antonio ended August 2004 with below normal rainfall for August.  

On the 1st, afternoon highs rose to the 90s, followed by an evening where scattered showers and thunderstorms moved in from the east. A significant lightning display accompanied the thunderstorms over the east part of South Central Texas between 8 and 11 pm on Sunday the 1st, as the area of rain and thunderstorms moved across the east and southeast part of South Central Texas, from a complex of afternoon to early evening convective storms over Southeast Texas. On Monday the 2nd, afternoon and evening showers and thunderstorms showed up again near San Antonio and west to Del Rio, then north across the hill country. On the 3rd, isolated showers and thunderstorms between Del Rio and Junction broke up quickly in the evening.

Hot afternoons prevailed on the 4th and 5th, as highs reached the Century Mark at Austin Bergstrom, with 100 on the 5th for the first time this year. At Austin Mabry a high of 101 was observed on August 5th, the 2nd 100 degree day of the year. The first 100 degree day this year at Austin Mabry was on Memorial Day, May 31st, when the high was 100. At Del Rio 3 days of 100 degree weather occurred the 4th to the 6th, with highs at 102 on the 5th and 6th. Highs at other locations at the Century Mark was as follows: Georgetown 102; Burnet 100; and San Marcos 100.

In the late afternoon and evening of Friday the 6th, showers and thunderstorms moved across the area from the north and northwest, causing 30 to 45 mph wind gusts in the evening at Del Rio and San Antonio. Locally heavy rains fell over parts of Kendall and Bexar County during the evening of the 6th.  A second wave of rain with showers and thunderstorms came from the north and northwest in the early to mid morning hours of Saturday the 7th. This area of showers and thunderstorms moved across the area in the day of Saturday the 7th. On Sunday the 8th, an area of rain with showers and thunderstorms came again in the early morning hours, ahead of a complex of storms further north over West Texas. Later in the day showers and thunderstorms returned. On Sunday evening the 8th, storms moved into the Del Rio area, where winds gusted to 44 mph and brief heavy rains fell. Rains moved into the Del Rio area again Monday the 9th. Heavy rains over the hill country the 7th and 8th, brought scattered near 1 to near 2 inch rains. Rains on Monday the 9th and Tuesday the 10th were mostly over the west part of South Central Texas.  Parts of Val Verde County received heavy rains on Monday the 9th.

A strong cold front for early August came across the area in the late afternoon and evening of August 11th. Scattered thunderstorms formed over the eastern parts of South Central Texas on the cold front in the late afternoon and evening hours. Damaging winds were reported over parts of Lee, Bastrop, and Fayette Counties. Much cooler days prevailed the 12th and 13th. Widely scattered showers and a few thunderstorms affected the west part of South Central Texas Friday the 13th, mainly between San Antonio and Del Rio. As this upper level disturbance moved east, mostly sunny conditions prevailed Saturday the 14th and again on Sunday the 15th. Isolated showers lingered over the west part of the area on the 15th.

Record breaking daily lows were observed from the 12th to the 18th at some locations.  On August 12th Austin Bergstrom had a record daily low of 64. On August 13th...a record low of 59 at Austin Bergstrom was observed, and a tie for the record low of 67 occurred at Del Rio.  On August 14th Austin Bergstrom tied the record daily low of 62, and broke the record daily low on the 15th with a low of 62.  On Monday the 16th, a record daily low of 59 was observed at Austin Bergstrom; 63 at San Antonio and 64 at Austin Mabry.  On August 17th and 18th, record daily lows of 61 and 64 respectively was observed at Austin Bergstrom International Airport. The 59 lows at Austin Bergstrom International Airport the 13th and 16th were also All Time August Lows for the Month of August.

Hot Mid to Late August highs on Friday the 20th, was followed by rainy conditions on the weekend of the 21st and 22nd. The shower and thunderstorm pattern extended into the morning hours of Monday, August 23rd. Flooding on roads at low water crossings was reported over Northwest Bexar County late Sunday evening the 22nd, and in Frio and Dimmit Counties on Monday morning the 23rd.  Scattered rainfall amounts of near a quarter to a half inch to near 2.5 inches was reported over the hill country. Rainfall amounts near 2 inches was reported in Dimmit County, and near 3 to 10.51 inch rains were reported in Frio Country.  Pearsall had 3.12 inches, while Dilley received 10.51 inches in about 12 hours. 

As the sub tropical high returned late the 23rd and on the 24th, afternoon highs warmed to near normal on the 24th, with highs reaching 100 at Del Rio.  Hot afternoons prevailed the 25th and 26th, with highs at 100 at Eagle Pass and 3 miles southwest of Carrizo Springs. On Thursday the 26th, mostly sunny and hot conditions prevailed, Del Rio returning to a high of 100. On Friday the 27th, the short lived subtropical high weakend, as widely scattered showers and thunderstorms formed over the west part of the area. On the weekend of the 28th and 29th scattered showers and thunderstorms formed over the area. Locally heavy rains formed over the hill country and the west to southwest part of South Central Texas on the 28th. The heaviest rains from the 28th included the following: La Pryor 3.93 inches; 11 miles south, southeast of Llano 2.38 inches; 9 miles west, southwest of Kingsland 2.02 inches; and 4 miles west of Manchaca 1.99 inches. On Sunday the 29th, widely scattered showers and thunderstorms returned once again. By Monday the 30th, the late summer shower pattern was mainly over the west half of South Central Texas. This trend continued on the last day of the month, the 31st, as Del Rio picked up 0.97 inches of rain from showers and thunderstorms in the afternoon and evening.

The average August temperature was 83.3 degrees, 0.9 degrees below normal. The average high was 93.3, and the average low was 73.4. Heating degree days 0 and cooling degree days 576. The highest temperature reached 99 on the 5th, and the lowest was 63 on the 16th.  Highest wind gust was 43 mph from the south, southeast with thunderstorms on the 18th. Rainfall was 1.10 inches, 1.47 inches below normal. Rainfall from January 1st to August 31st, 2004... 24.40 inches or 2.88 inches above normal.