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September Weather in Saint Johns, United States

Last updated: June 24, 2025

In September, the average temperature in Saint Johns, United States is a comfortable 18°C (65°F). However, be prepared for a range as temperatures can dip to a chilly 2°C (35°F) or soar up to a sweltering 35°C (95°F). Rain is likely, with 101 mm (4.0 in) of precipitation spread over about 11 days, and you can expect a fairly high humidity level at 80%.

September Temperature in Saint Johns

In September in Saint Johns, the average temperature is 18°C (65°F). Maximum temperatures can reach 35°C (95°F), while minimums can drop as low as 2°C (35°F). Be prepared for a wide range of temperatures during your travels, so pack accordingly!

September Weather in Saint Johns: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Saint Johns, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Saint Johns, September typically has an average temperature of 18°C (65°F), with highs reaching up to 35°C (95°F) and lows dropping to around 2°C (35°F).
JanFebMarAprMayJunJulAugSepOctNovDec252736465970757265533832
Data source: Temperature data for Saint Johns 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 Saint Johns

In Saint Johns in September, the precipitation amount is 101 mm (4.0 in) spread over 11 days.

September Precipitation Trends in Saint Johns

The chart displays monthly precipitation patterns in Saint Johns, 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 Saint Johns, September typically receives around 101 mm (4.0 inches) of precipitation spread over approximately 11 days.
JanFebMarAprMayJunJulAugSepOctNovDec6366638812111768681011166360
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Saint Johns

In Saint Johns in September, humidity is 80%. With an average temperature of 18°C (65°F), this humidity feels like wandering through a warm, damp blanket, making every step slightly heavy and resulting in a constant sheen of sweat, which can be both refreshing and exhausting for travelers.

September Average Humidity in Saint Johns

This chart illustrates the average monthly humidity levels in Saint Johns, 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 Saint Johns is approximately 80%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec88%87%85%86%80%80%80%81%80%84%90%86%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Saint Johns

In Saint Johns 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 Saint Johns.

Maximum UV Index Levels in Saint Johns for September

The chart shows the monthly maximum UV Index (UVI) for Saint Johns 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 Saint Johns typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec24589101097532
Data source: Saint Johns 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 Saint Johns Compares to Other Months

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

This table compares monthly weather conditions in Saint Johns, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-4°C (26°F)63 mm (2.5 inches)88%low
February Weather-3°C (27°F)66 mm (2.6 inches)87%moderate
March Weather2°C (36°F)63 mm (2.5 inches)85%moderate
April Weather8°C (47°F)88 mm (3.5 inches)86%very high
May Weather15°C (60°F)121 mm (4.8 inches)80%very high
June Weather21°C (70°F)117 mm (4.6 inches)80%very high
July Weather24°C (75°F)68 mm (2.7 inches)80%very high
August Weather22°C (72°F)68 mm (2.7 inches)80%very high
September Weather18°C (65°F)101 mm (4.0 inches)80%high
October Weather12°C (53°F)116 mm (4.6 inches)84%moderate
November Weather3°C (38°F)63 mm (2.5 inches)89%moderate
December Weather0°C (32°F)60 mm (2.4 inches)86%low

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