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September Weather in Heidelberg, United States

Last updated: June 24, 2025

In Heidelberg, United States, the average temperature in September hovers around 26°C (78°F), with a notable range from a cool 11°C (52°F) to a scorching 38°C (102°F). You can expect 97 mm (3.8 in) of precipitation spread over 10 days, contributing to the region's average humidity of 80%. Be prepared for a mix of warm days and occasional showers!

September Temperature in Heidelberg

In September in Heidelberg, the average temperature is 26°C (78°F). Maximums can reach 38°C (102°F), while minimums can drop as low as 11°C (52°F). Overall, this makes Heidelberg a great destination for travelers seeking warm weather with a range of temperatures for various activities.

September Weather in Heidelberg: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Heidelberg, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Heidelberg, September typically has an average temperature of 26°C (78°F), with highs reaching up to 38°C (102°F) and lows dropping to around 11°C (52°F).
JanFebMarAprMayJunJulAugSepOctNovDec495561657479818178705652
Data source: Temperature data for Heidelberg 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 Heidelberg

In Heidelberg in September, the total precipitation amount is 97 mm (3.8 in) over a span of 10 days.

September Precipitation Trends in Heidelberg

The chart displays monthly precipitation patterns in Heidelberg, 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 Heidelberg, September typically receives around 97 mm (3.8 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec110140121127137168137132979972133
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Heidelberg

In Heidelberg in September, humidity is 80%. With an average temperature of 26°C (78°F), this humidity feels like a warm blanket enveloping you, making travel a bit sticky yet vibrant, as you experience the lively atmosphere infused with the scent of tropical blooms and the soothing presence of nearby water.

September Average Humidity in Heidelberg

This chart illustrates the average monthly humidity levels in Heidelberg, 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 Heidelberg is approximately 80%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec82%80%80%78%73%71%79%78%80%76%83%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Heidelberg

In Heidelberg 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 Heidelberg.

Maximum UV Index Levels in Heidelberg for September

The chart shows the monthly maximum UV Index (UVI) for Heidelberg 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 Heidelberg typically reaches 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec478111111111110864
Data source: Heidelberg 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 Heidelberg Compares to Other Months

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

This table compares monthly weather conditions in Heidelberg, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather10°C (50°F)110 mm (4.3 inches)82%moderate
February Weather13°C (55°F)140 mm (5.5 inches)80%high
March Weather16°C (61°F)121 mm (4.7 inches)80%very high
April Weather18°C (65°F)127 mm (5.0 inches)78%extreme
May Weather23°C (74°F)137 mm (5.4 inches)73%extreme
June Weather26°C (79°F)168 mm (6.6 inches)71%extreme
July Weather27°C (81°F)137 mm (5.4 inches)79%extreme
August Weather27°C (81°F)132 mm (5.2 inches)78%extreme
September Weather26°C (78°F)97 mm (3.8 inches)80%very high
October Weather21°C (70°F)99 mm (3.9 inches)76%very high
November Weather13°C (56°F)72 mm (2.8 inches)83%high
December Weather11°C (53°F)133 mm (5.3 inches)87%moderate

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