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September Weather in Grantham, United States

Last updated: June 24, 2025

In Grantham, United States, the average temperature in September hovers around 17°C (62°F). Expect a thrilling range, with minimums that can dip to -2°C (28°F) and maximums soaring up to 32°C (89°F). This month sees about 64 mm (2.5 in) of precipitation over 8 days, contributing to an average humidity of 71%. Stay prepared for a mix of weather!

September Temperature in Grantham

In September in Grantham, the average temperature is 17°C (62°F), with maximums reaching up to 32°C (89°F) and minimums plummeting as low as -2°C (28°F). Travelers should be prepared for a wide range of temperatures during this month.

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

The chart illustrates September temperature patterns in Grantham, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Grantham, September typically has an average temperature of 17°C (62°F), with highs reaching up to 32°C (89°F) and lows dropping to around -2°C (28°F).
JanFebMarAprMayJunJulAugSepOctNovDec222532445666716962503626
Data source: Temperature data for Grantham 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 Grantham

In Grantham in September, the precipitation amount is 64 mm (2.5 in) over the course of 8 days.

September Precipitation Trends in Grantham

The chart displays monthly precipitation patterns in Grantham, 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 Grantham, September typically receives around 64 mm (2.5 inches) of precipitation spread over approximately 8 days.
JanFebMarAprMayJunJulAugSepOctNovDec70817111678851208664132100102
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Grantham

In Grantham in September, humidity is 71%. With an average temperature of 17°C (62°F), this humidity feels like a warm embrace that can leave you feeling a bit sticky, making outdoor exploration both refreshing and slightly uncomfortable.

September Average Humidity in Grantham

This chart illustrates the average monthly humidity levels in Grantham, 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 Grantham is approximately 71%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%84%82%80%72%72%67%66%71%79%84%81%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Grantham

In Grantham in September, the maximum UV index is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more detailed information, you can check the Hourly UV Index in Grantham.

Maximum UV Index Levels in Grantham for September

The chart shows the monthly maximum UV Index (UVI) for Grantham 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 Grantham typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3468910997532
Data source: Grantham 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 Grantham Compares to Other Months

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

This table compares monthly weather conditions in Grantham, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-6°C (22°F)70 mm (2.7 inches)86%moderate
February Weather-4°C (25°F)81 mm (3.2 inches)84%moderate
March Weather0°C (32°F)71 mm (2.8 inches)82%high
April Weather6°C (44°F)116 mm (4.6 inches)80%very high
May Weather13°C (56°F)78 mm (3.1 inches)72%very high
June Weather19°C (66°F)85 mm (3.4 inches)72%very high
July Weather22°C (71°F)120 mm (4.7 inches)67%very high
August Weather21°C (69°F)86 mm (3.4 inches)66%very high
September Weather17°C (62°F)64 mm (2.5 inches)71%high
October Weather10°C (50°F)132 mm (5.2 inches)78%moderate
November Weather2°C (36°F)100 mm (3.9 inches)84%moderate
December Weather-3°C (27°F)102 mm (4.0 inches)81%low

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