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September Weather in Round Rock, United States

Last updated: June 24, 2025

In Round Rock, United States, the average temperature in September hovers around 21°C (69°F). However, be prepared for a range, as temperatures can dip to a chilly 1°C (34°F) or soar to a sizzling 35°C (96°F). With a precipitation amount of 12 mm (0.5 in) spread over 3 days, it’s wise to bring an umbrella. Expect an average humidity level of 59%, providing a comfortable atmosphere for exploration.

September Temperature in Round Rock

In September in Round Rock, the average temperature is 21°C (69°F), with maximums reaching up to 35°C (96°F) and minimums dipping as low as 1°C (34°F). This diverse range of temperatures makes Round Rock an ideal destination for travelers seeking both warm days and cooler evenings.

September Weather in Round Rock: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Round Rock, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Round Rock, September typically has an average temperature of 21°C (69°F), with highs reaching up to 35°C (96°F) and lows dropping to around 1°C (34°F).
JanFebMarAprMayJunJulAugSepOctNovDec323846556376797869544433
Data source: Temperature data for Round Rock generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Round Rock

In Round Rock in September, the precipitation amount is 12 mm (0.5 in) during a span of 3 days.

September Precipitation Trends in Round Rock

The chart displays monthly precipitation patterns in Round Rock, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In Round Rock, September typically receives around 12 mm (0.5 inches) of precipitation spread over approximately 3 days.
JanFebMarAprMayJunJulAugSepOctNovDec2222321014314512211022
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Round Rock

In Round Rock in September, humidity is 59%. With an average temperature of 21°C (69°F), this humidity feels like a comfortable embrace, making it ideal for exploring local attractions without the discomfort of excessive heat or stickiness.

September Average Humidity in Round Rock

This chart illustrates the average monthly humidity levels in Round Rock, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in Round Rock is approximately 59%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec85%86%76%69%53%40%36%44%59%74%83%86%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Round Rock

In Round Rock in September, the maximum UV index reaches 11, which corresponds to an extreme Exposure Category. With a time to burn of just 10 minutes, it's essential to take precautions. For more details, you can check the Hourly UV Index in Round Rock.

Maximum UV Index Levels in Round Rock for September

The chart shows the monthly maximum UV Index (UVI) for Round Rock in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In September, the maximum UV index in Round Rock typically reaches 11, which falls under the extreme exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec479111213131211864
Data source: Round Rock September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How September Weather in Round Rock Compares to Other Months

Weather in Round Rock varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Round Rock, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Round Rock, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather0°C (33°F)22 mm (0.9 inches)85%moderate
February Weather3°C (38°F)22 mm (0.9 inches)86%high
March Weather8°C (46°F)31 mm (1.2 inches)76%very high
April Weather13°C (55°F)10 mm (0.4 inches)69%extreme
May Weather17°C (63°F)14 mm (0.6 inches)53%extreme
June Weather24°C (76°F)3 mm (0.1 inches)40%extreme
July Weather26°C (80°F)14 mm (0.5 inches)36%extreme
August Weather25°C (78°F)4 mm (0.2 inches)44%extreme
September Weather21°C (69°F)12 mm (0.5 inches)59%extreme
October Weather12°C (54°F)21 mm (0.8 inches)74%very high
November Weather7°C (44°F)10 mm (0.4 inches)83%high
December Weather1°C (34°F)22 mm (0.8 inches)85%moderate

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