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September Weather in Clear Lake, United States

Last updated: June 24, 2025

In Clear Lake, United States, the average temperature in September is a comfortable 18°C (65°F). However, be prepared for variability, as temperatures can dip as low as 3°C (37°F) and peak at a warm 33°C (92°F). Expect about 105 mm (4.1 in) of precipitation spread over 10 days, and enjoy a typically humid atmosphere with an average humidity of 75%.

September Temperature in Clear Lake

In September in Clear Lake, the average temperature is 18°C (65°F), with maximums that can reach 33°C (92°F) and minimums that can drop to as low as 3°C (37°F). Overall, travelers should be prepared for a range of temperatures, ensuring they pack both warm clothing for the cooler evenings and lighter attire for the hotter days.

September Weather in Clear Lake: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Clear Lake, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Clear Lake, September typically has an average temperature of 18°C (65°F), with highs reaching up to 33°C (92°F) and lows dropping to around 3°C (37°F).
JanFebMarAprMayJunJulAugSepOctNovDec181834456072747065493527
Data source: Temperature data for Clear Lake 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 Clear Lake

In Clear Lake in September, the precipitation amount is 105 mm (4.1 in) over the course of 10 days.

September Precipitation Trends in Clear Lake

The chart displays monthly precipitation patterns in Clear Lake, 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 Clear Lake, September typically receives around 105 mm (4.1 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec364772831591331021211051104736
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Clear Lake

In Clear Lake in September, humidity is 75%. With an average temperature of 18°C (65°F), this humidity feels like a warm, enveloping blanket that can make outdoor exploration feel a bit stifling, potentially leading to discomfort during travel activities.

September Average Humidity in Clear Lake

This chart illustrates the average monthly humidity levels in Clear Lake, 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 Clear Lake is approximately 75%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec82%84%80%81%74%81%80%77%75%80%87%83%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Clear Lake

In Clear Lake in September, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in Clear Lake.

Maximum UV Index Levels in Clear Lake for September

The chart shows the monthly maximum UV Index (UVI) for Clear Lake 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 Clear Lake typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec35589111098533
Data source: Clear Lake 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 Clear Lake Compares to Other Months

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

This table compares monthly weather conditions in Clear Lake, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-8°C (19°F)36 mm (1.4 inches)82%moderate
February Weather-8°C (18°F)47 mm (1.9 inches)84%moderate
March Weather1°C (35°F)72 mm (2.9 inches)80%moderate
April Weather7°C (45°F)83 mm (3.3 inches)81%very high
May Weather15°C (60°F)159 mm (6.2 inches)74%very high
June Weather22°C (72°F)133 mm (5.2 inches)80%extreme
July Weather23°C (74°F)102 mm (4.0 inches)80%very high
August Weather21°C (71°F)121 mm (4.8 inches)77%very high
September Weather18°C (65°F)105 mm (4.1 inches)75%very high
October Weather10°C (49°F)110 mm (4.3 inches)80%moderate
November Weather2°C (35°F)47 mm (1.9 inches)87%moderate
December Weather-3°C (27°F)36 mm (1.4 inches)83%moderate

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