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September Weather in Round Rock, United States

Last updated: June 24, 2025

In September, the average temperature in Round Rock, United States hovers around 26°C (80°F), offering a pleasant climate for visitors. However, temperatures can vary significantly, dipping to a chilly 11°C (52°F) and soaring to a sweltering 38°C (101°F). With an average precipitation of 109 mm (4.3 in) spread over 10 days, you might want to pack an umbrella. Additionally, the air maintains an average humidity of 66%, making it feel a bit more vibrant and alive.

September Temperature in Round Rock

In September in Round Rock, the average temperature is 26°C (80°F), with maximums reaching 38°C (101°F) and minimums dipping as low as 11°C (52°F). Be prepared for warm days, but also bring layers for 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 26°C (80°F), with highs reaching up to 38°C (101°F) and lows dropping to around 11°C (52°F).
JanFebMarAprMayJunJulAugSepOctNovDec515363687682858680705954
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 109 mm (4.3 in) spread over 10 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 109 mm (4.3 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec476067881557669103109904669
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 66%. With an average temperature of 26°C (80°F), this humidity feels like a warm, sticky embrace, making travel a bit challenging as you might find yourself needing frequent breaks to cool down and stay hydrated.

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 66%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec78%78%77%78%82%78%69%63%66%73%84%87%
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 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more detailed information, 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 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec589111112121110965
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 Weather11°C (51°F)47 mm (1.9 inches)78%moderate
February Weather11°C (53°F)60 mm (2.4 inches)78%very high
March Weather17°C (63°F)67 mm (2.6 inches)77%very high
April Weather20°C (68°F)88 mm (3.5 inches)78%extreme
May Weather25°C (76°F)155 mm (6.1 inches)82%extreme
June Weather28°C (82°F)76 mm (3.0 inches)78%extreme
July Weather30°C (85°F)69 mm (2.7 inches)69%extreme
August Weather30°C (86°F)103 mm (4.0 inches)63%extreme
September Weather26°C (80°F)109 mm (4.3 inches)66%very high
October Weather21°C (70°F)90 mm (3.5 inches)73%very high
November Weather15°C (60°F)46 mm (1.8 inches)84%high
December Weather12°C (55°F)69 mm (2.7 inches)87%moderate

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