September weather forecastSan Marcos, TX
September
Weather in September
September, the first month of the autumn in San Marcos, is still a tropical month, with an average temperature ranging between max 88°F (31.1°C) and min 70.5°F (21.4°C).Temperature
In San Marcos, entering September brings a subtle temperature decrement, reducing from August's very hot 95.9°F (35.5°C) to a tropical 88°F (31.1°C). Throughout September, an average nighttime temperature of 70.5°F (21.4°C) is experienced.Heat index
For September, the heat index is appraised at a very hot 100.4°F (38°C). Adopt enhanced safety measures, heat exhaustion and heat cramps could occur. Continuous activity may induce heatstroke.It is essential to grasp that the heat index's numbers are for shade and light wind settings. Exposing to direct sunshine may enhance heat index values by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature' or 'real feel', binds temperature metrics with humidity values to give a sense of the actual warmth. The effect is experienced differently by individuals, hinging on unique characteristics such as body mass, stature, and level of activity. When you're directly under the sun's rays, remember that the heat index may surge by 15 Fahrenheit (8 Celsius) degrees. Heat index values are essentially critical for children. Young individuals usually face greater risks than adults as their sweat production is less. Also, their larger skin surface relative to their small bodies and the high heat generation due to their activity contributes to their vulnerability.
The natural cooling mechanism in humans involves perspiration, where the evaporation of sweat balances out excessive warmth. Increased relative humidity slows down evaporation, thereby decreasing the rate of heat removal from the body, culminating in a sensation of overheating. When the heat gained surpasses the body's cooling capacity, temperatures rise, signaling potential health concerns.
Humidity
In September, the average relative humidity is 70%.Rainfall
In San Marcos, in September, it is raining for 15.5 days, with typically 3.62" (92mm) of accumulated precipitation. In San Marcos, during the entire year, the rain falls for 151.8 days and collects up to 26.89" (683mm) of precipitation.Snowfall
In San Marcos, snow does not fall in March through November.Daylight
The average length of the day in September is 12h and 20min.On the first day of the month, sunrise is at 7:09 am and sunset at 7:53 pm. On the last day of September, sunrise is at 7:24 am and sunset at 7:18 pm CDT.
Sunshine
The average sunshine in September is 8.3h.UV index
In San Marcos, the average daily maximum UV index in September is 6. A UV Index reading of 6 to 7 represents a high health vulnerability from unprotected exposure to Sun's UV rays for ordinary individuals.Note: The daily high UV index of 6 during September translates into the following recommendations:
Resist extreme sun exposure. Guarding against solar damage is essential. The Sun's UV radiation is at its strongest between the hours of 10 a.m. and 4 p.m. Minimize direct exposure to the sun during this period. In the presence of strong sunlight, it's crucial to wear sunglasses that ward off UVA and UVB rays.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
San Marcos, TX
- Average high temperature in September: 88°F
The warmest month (with the highest average high temperature) is August (95.9°F).
The month with the lowest average high temperature is January (59.9°F).
- Average low temperature in September: 70.5°F
The month with the highest average low temperature is August (74.7°F).
The coldest month (with the lowest average low temperature) is January (42.8°F).
Average pressure in September
San Marcos, TX
- Average pressure in September: 29.95"Hg
The month with the highest atmospheric pressure is January (30.15"Hg).
The month with the lowest atmospheric pressure is June (29.9"Hg).
Average wind speed in September
San Marcos, TX
- Average wind speed in September: 6.1mph
The windiest month (with the highest average wind speed) is February (9.1mph).
The calmest month (with the lowest average wind speed) is September (6.1mph).
Average humidity in September
San Marcos, TX
- Average humidity in September: 70%
The month with the highest relative humidity is May (77%).
The month with the lowest relative humidity is August (62%).
Average rainfall in September
San Marcos, TX
- Average rainfall in September: 3.62"
The wettest month (with the highest rainfall) is May (4.57").
The driest month (with the least rainfall) is February (1.1").
Average rainfall days in September
San Marcos, TX
- Average rainfall days in September: 15.5 days
The month with the highest number of rainy days is May (16.6 days).
The month with the least rainy days is January (9.4 days).
Average snowfall in September
San Marcos, TX
- Average snowfall in September: 0"
The months with the highest snowfall are January and February (0.12").
The months with the least snowfall are March, April, May, June, July, August, September, October and November (0").
Average snowfall days in September
San Marcos, 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 Marcos, 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 18min
The months with the most sunshine are July and August (Average sunshine: 10h and 0min).
The month with the least sunshine is December (Average sunshine: 5h and 12min).
Average sunshine days in September
San Marcos, TX
- Average sunshine days in September: 12.4 days
The month with the most sunshine days is January (19.4 days).
The month with the least sunshine days is May (11.9 days).
Average UV index in September
San Marcos, 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 Marcos, TX
- Average cloud cover in September: 34
The month with the most cloud cover is March (Cloud cover 49).
The month with the least cloud cover is August (Cloud cover 25).
Average visibility in September
San Marcos, TX
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, June, July, August, September, October, November and December (6mi).
The month with the lowest visibility is May (5mi).
