The average September temperature was 76.7 degrees, 2.7 degrees below normal. September 2003 tied with September 1903, as the 9th coolest September of record for San Antonio. The average high was 85.7, and the average low was 67.7. Heating degree days 0 and Cooling degree days 357. The highest temperature reached 94 on the 10th. The lowest was 57 on the 30th. Highest wind gust was 31 mph from the north with thunderstorms on the 11th. Rainfall was 9.21 inches, 6.21 inches above normal and was the 6th wettest September of record. Rainfall from January 1st to September 30th, 2003... 26.08 inches or 1.56 inches above normal.

A series of rain making weather systems coming out of the west and northwest, accompanied by weak cool fronts, plus a dry cool front in the last few days of the month, helped to make September 2003 cooler than normal for parts of Central and South Central Texas. September 2003 was the 4th coolest September of record for Austin Bergstrom International Airport, and tied with September 1903 for the 9th coolest September of record for San Antonio. Most of the area had above normal rainfall for September; however, a few locations over the northern Texas Hill Country, then east to parts of Central Texas had rainfall slightly below normal. As the weak cool fronts slowed down further south and interacted with more gulf moisture, the heavier rains and showers were more widespread. A few hot summer like days came in the early part of September; however, as the month continued to mid and late September, daytime highs steadily cooled off, as weak frontal systems brought rain and showers to the area, followed by a dry cool front in the last several days of the month. Compared to past Septembers, there were not many hot days in September 2003. The 9.21 inches of rain at San Antonio International Airport made September 2003 the 6th wettest of record for San Antonio.

On the 1st day of the month widely scattered showers and thunderstorms showed up over parts of Central Texas. On the next day showers and thunderstorms showed up over eastern parts of South Central Texas, and then expanded westward and increased in area coverage on Wednesday the 3rd. The rainy pattern continued the 4th and 5th. Locally heavy rains came on Friday the 5th to parts of the Texas Hill Country and extended southward to San Antonio, parts of Medina County, parts of Wilson County and parts of Atascosa County. Locally heavy rains in the San Antonio Area on Friday the 5th caused some streets to get flooded.

On the weekend of the 6th and 7th more stable conditions emerged as rain and shower activity eased. A dry and warm period stretched from the 6th through the 9th. This pattern did not last long though, as another wet period followed shortly thereafter. An upper air disturbance from the north and west brought periods of rain, showers and thunderstorms to the area from the 10th to the morning of the 12th. The rain began the 10th and 11th across the northern parts of the area, over the Texas Hill Country and parts of Central Texas. A line of showers and thunderstorms formed the evening of the 11th, and moved south and southeast across the Texas Hill Country, parts of Central Texas and South Central Texas, leaving locally heavy rains the night of the 11th and early morning of the 12th. Some of the thunderstorms caused high winds. High winds were observed over Llano and Comal County, and also in the Del Rio Area on the evening of Thursday, September 11th. Some flooded low water crossings resulted, as the rains came down quickly. Skies cleared out in the late morning and afternoon of Friday the 12th.

Partly cloudy conditions on the 13th did not last long, as a rapidly approaching upper level disturbance coming from the northwest caused increasing clouds the night of the 13th. This was followed by a wave of rain, with mostly showers and isolated thunderstorms on Sunday the 14th, as a weather system came quickly from the northwest to southeast. Skies cleared up in the afternoon and evening of the 14th. On the 15th and 16th, partly cloudy days prevailed in wake of the rains on Sunday the 14th.

On the night of the 16th and early morning of the 17th, humidity increased rapidly again, ahead of a rain making system coming from the west. Rainy weather returned the 17th, and the rains continued on Thursday the 18th. An area of showers and thunderstorms north and west of the area, came south and east, bringing rains to the area Thursday the 18th. A weak cool front followed Friday the 19th. Skies briefly cleared up on Friday the 19th, and then were followed by cloudy conditions the night of the 19th, and clouds lingered through the next day of Saturday the 20th, as another upper air disturbance approached from the west and northwest, interacting with moisture coming from the south and southwest. This resulted in a cloudy and cool day on Saturday the 20th, in wake of the cool front on the 19th. The rains continued the night of the 20th, and into the morning hours of Sunday the 21st, as mostly light to moderate rain. Skies cleared up the night of the 21st through the early morning of the 22nd.

On Monday the 22nd, after brief patchy early morning fog,   mostly sunny skies and drier weather in the day came to South Central Texas.  Scattered high clouds began to come over the area in the day of Monday the 22nd, and also Tuesday the 23rd, from  convective debris aloft associated with Hurricane Marty to the west. On the 24th, the high level clouds thinned out, and scattered low clouds in the day prevailed in a stable environment. On the night of the 24th and early morning of the 25th, humidity increased markedly ahead of another rain making weather system.

On the night of the 25th, another weather system came out of the northwest and moved rapidly southeast, bringing a wave of rain with showers and isolated thunderstorms the night of the 25th and morning of the 26th. Skies cleared up in the afternoon of the 26th. On the night of the 26th and early morning the 27th, isolated showers and thunderstorms moved from near Del Rio to near and mainly west of Laredo. A cool front came through the area from the northeast in the day of Saturday September 27th, and brought slightly drier air to the area. On the 28th through the 30th, dry and stable weather prevailed. The coolest temperatures of the month came on the last day, in the early morning hours, as lows were in the 50s, with some areas reporting near 50 over the Texas Hill Country and parts of Central Texas. The last 2 days of the month were mostly clear, with sunny and pleasant days to clear and cool nights.