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September Weather in Saint John, United States

Last updated: June 24, 2025

In Saint John, United States, the average temperature in September hovers around 22°C (73°F), offering a pleasant climate for outdoor activities. However, temperatures can fluctuate, with minimums dipping to 7°C (45°F) and maximums soaring to 35°C (95°F). Expect around 56 mm (2.2 in) of precipitation over 7 days, contributing to an average humidity of 76%, creating a lush and vibrant environment.

September Temperature in Saint John

In September in Saint John, the average temperature is 22°C (73°F). Maximums can reach 35°C (95°F) and minimums can be as low as 7°C (45°F). Be prepared for a warm climate with the possibility of cooler evenings, making it an ideal time to explore outdoor activities.

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

The chart illustrates September temperature patterns in Saint John, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Saint John, September typically has an average temperature of 22°C (73°F), with highs reaching up to 35°C (95°F) and lows dropping to around 7°C (45°F).
JanFebMarAprMayJunJulAugSepOctNovDec323547556777807672594439
Data source: Temperature data for Saint John 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 John

In Saint John in September, the total precipitation amount is 56 mm (2.2 in) over a period of 7 days.

September Precipitation Trends in Saint John

The chart displays monthly precipitation patterns in Saint John, 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 John, September typically receives around 56 mm (2.2 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec768013112914510197130561057559
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Saint John

In Saint John in September, humidity is 76%. With an average temperature of 22°C (73°F), this humidity feels like a warm embrace that envelops you, making travel both refreshing and slightly steamy, as the air clings warmly to your skin.

September Average Humidity in Saint John

This chart illustrates the average monthly humidity levels in Saint John, 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 John is approximately 76%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec82%80%80%80%82%83%81%80%76%76%85%86%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Saint John

In Saint John in September, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Saint John.

Maximum UV Index Levels in Saint John for September

The chart shows the monthly maximum UV Index (UVI) for Saint John 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 John typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3569101110109643
Data source: Saint John 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 John Compares to Other Months

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

This table compares monthly weather conditions in Saint John, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather0°C (32°F)76 mm (3.0 inches)82%moderate
February Weather2°C (35°F)80 mm (3.2 inches)80%moderate
March Weather8°C (47°F)131 mm (5.2 inches)80%high
April Weather13°C (55°F)129 mm (5.1 inches)80%very high
May Weather20°C (68°F)145 mm (5.7 inches)82%very high
June Weather25°C (77°F)101 mm (4.0 inches)83%extreme
July Weather26°C (80°F)97 mm (3.8 inches)81%very high
August Weather25°C (76°F)130 mm (5.1 inches)80%very high
September Weather22°C (73°F)56 mm (2.2 inches)76%very high
October Weather15°C (59°F)105 mm (4.1 inches)76%high
November Weather7°C (44°F)75 mm (2.9 inches)85%moderate
December Weather4°C (39°F)59 mm (2.3 inches)86%moderate

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