September weather forecastSan Antonio, TX
September
Weather in September
With September, San Antonio transitions from the intense summer heat to relatively cooler days. However, this month sees a significant increase in average rainfall from 1.5in in August to 3.39in in September. Despite the onset of autumn, the city remains warm and attracts visitors seeking late summer vacations. September marks the beginning of the shift from summer to fall, with balmy evenings perfect for leisurely strolls.Temperature
September indicates a minor shift in the average high-temperature, from August's fiery hot 96.6°F (35.9°C) to a hot 89.1°F (31.7°C). An average temperature of 71.6°F (22°C) is recorded during the nights in September.Heat index
In September, the heat index is computed to be a fiery hot 100.4°F (38°C). Heightened safety actions are necessary, heat cramps and heat exhaustion are probable. Persistent activity may lead to heatstroke.From a standpoint of the heat index, values pertain to shaded conditions and mild breezes. Being exposed to direct sunshine might trigger a heat index increase by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like' or 'apparent temperature', combines air temperature and relative humidity to represent a human perceived temperature equivalent. The influence of weather is personal, with varied individuals experiencing it differently due to differences in body mass, stature, and physical exertion levels. When exposed to direct sunlight, it's possible for the heat index to increase by as much as 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly meaningful for babies and toddlers. Children often do not understand the need to rest and hydrate. Thirst is a late manifestation of dehydration - therefore, it is essential to stay hydrated, particularly during prolonged physical activities.
In response to overheating, the human body perspires to cool down, mainly through the evaporation of sweat. A higher relative humidity affects normal body cooling by reducing the evaporation rate, subsequently lowering the rate at which the body cools and increasing the perception of heat. Heat absorption that surpasses the body's shedding capability can lead to overheating and varying levels of dehydration.
Humidity
In San Antonio, the average relative humidity in September is 66%.Rainfall
In San Antonio, during September, the rain falls for 17 days and regularly aggregates up to 3.39" (86mm) of precipitation. Throughout the year, in San Antonio, there are 144.5 rainfall days, and 22.6" (574mm) of precipitation is accumulated.Snowfall
In San Antonio, snow does not fall in March through November.Daylight
In September, the average length of the day is 12h and 20min.On the first day of the month, sunrise is at 7:11 am and sunset at 7:55 pm. On the last day of September, sunrise is at 7:27 am and sunset at 7:20 pm CDT.
Sunshine
The average sunshine in September is 8.4h.UV index
In San Antonio, the average daily maximum UV index in September is 6. A UV Index value of 6 to 7 symbolizes a high health hazard from unsafe exposure to UV radiation for average individuals.Note: The UV index of 6 in September translates into these instructions:
Enforce precautions and stick to sun safety measures. Preservation from skin and eye damage is essential. Stay in the shade and limit direct sun exposure between 10 a.m. and 4 p.m., when UV radiation is at its strongest. Remember, however, that not all shade structures provide full sun protection. To mitigate harm from sun exposure, pick sunglasses offering UVA and UVB defense.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
San Antonio, TX
- Average high temperature in September: 89.1°F
The warmest month (with the highest average high temperature) is August (96.6°F).
The month with the lowest average high temperature is January (61.7°F).
- Average low temperature in September: 71.6°F
The month with the highest average low temperature is August (75.7°F).
The coldest month (with the lowest average low temperature) is January (44.2°F).
Average pressure in September
San Antonio, TX
- Average pressure in September: 29.94"Hg
The month with the highest atmospheric pressure is January (30.15"Hg).
The month with the lowest atmospheric pressure is June (29.89"Hg).
Average wind speed in September
San Antonio, TX
- Average wind speed in September: 6.5mph
The windiest month (with the highest average wind speed) is May (9mph).
The calmest month (with the lowest average wind speed) is September (6.5mph).
Average humidity in September
San Antonio, TX
- Average humidity in September: 66%
The month with the highest relative humidity is May (73%).
The month with the lowest relative humidity is August (59%).
Average rainfall in September
San Antonio, TX
- Average rainfall in September: 3.39"
The wettest month (with the highest rainfall) is May (3.66").
The driest month (with the least rainfall) is February (0.98").
Average rainfall days in September
San Antonio, TX
- Average rainfall days in September: 17 days
The month with the highest number of rainy days is September (17 days).
The month with the least rainy days is January (9.1 days).
Average snowfall in September
San Antonio, TX
- Average snowfall in September: 0"
The months with the highest snowfall are January and February (0.08").
The months with the least snowfall are March, April, May, June, July, August, September, October and November (0").
Average snowfall days in September
San Antonio, TX
- Average snowfall days in September: 0 days
The months with the highest number of snowfall days are January and February (0.3 days).
The months with the least snowfall days are March, April, May, June, July, August, September, October and November (0 days).
Average daylight in September /
Average sunshine in September
San Antonio, TX
- Average daylight in September: 12h and 18min
The month with the longest days is June (Average daylight: 14h and 0min).
The month with the shortest days is December (Average daylight: 10h and 18min).
- Average sunshine in September: 8h and 24min
The month with the most sunshine is July (Average sunshine: 10h and 18min).
The month with the least sunshine is December (Average sunshine: 5h and 18min).
Average sunshine days in September
San Antonio, TX
- Average sunshine days in September: 11.8 days
The month with the most sunshine days is January (20.3 days).
The months with the least sunshine days are May and September (11.8 days).
Average UV index in September
San Antonio, TX
- Average UV index in September: 6
The months with the highest UV index are June, July and August (UV index 7).
The month with the lowest UV index is December (UV index 3).
Average cloud cover in September
San Antonio, TX
- Average cloud cover in September: 33
The month with the most cloud cover is March (Cloud cover 47).
The month with the least cloud cover is August (Cloud cover 23).
Average visibility in September
San Antonio, TX
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
