September Weather in Saint John, United States

Last updated: June 24, 2025

In Saint John, United States, the average temperature in September hovers around 23°C (73°F), with minimums diving to 5°C (41°F) and highs peaking at 37°C (99°F). Expect 62 mm (2.4 in) of precipitation over 7 days, complemented by an average humidity of 67%. Enjoy the blend of warmth and moisture as you explore the unique ambiance this month has to offer!

September Temperature in Saint John

In September in Saint John, the average temperature is 23°C (73°F), with maximums reaching up to 37°C (99°F) and minimums dropping as low as 5°C (41°F). This makes it essential for travelers to pack for both warm and cool conditions.

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 23°C (73°F), with highs reaching up to 37°C (99°F) and lows dropping to around 5°C (41°F).

Data source: Temperature data for Saint John generated using information from the Copernicus Climate Change Service.

September Precipitation in Saint John

In Saint John in September, the total precipitation amount is 62 mm (2.4 in) observed over a span 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 62 mm (2.4 inches) of precipitation spread over approximately 7 days.

Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

September Humidity in Saint John

In Saint John in September humidity is 67%. With an average temperature of 23°C (73°F), this humidity feels like a warm, enveloping blanket that makes the air feel thick and slightly sticky, which can be challenging for travelers who prefer cooler, drier conditions.

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 67%, offering insight into how humid the weather typically is during this month.

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.

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.
	Temperature	Precipitation	Humidity	UV
January Weather	0°C (33°F)	25 mm (1.0 inches)	75%	moderate
February Weather	1°C (34°F)	21 mm (0.8 inches)	76%	moderate
March Weather	8°C (47°F)	68 mm (2.7 inches)	67%	high
April Weather	12°C (54°F)	50 mm (2.0 inches)	70%	very high
May Weather	18°C (65°F)	168 mm (6.6 inches)	82%	very high
June Weather	25°C (77°F)	62 mm (2.4 inches)	82%	extreme
July Weather	27°C (81°F)	58 mm (2.3 inches)	81%	extreme
August Weather	25°C (78°F)	74 mm (2.9 inches)	76%	very high
September Weather	23°C (73°F)	62 mm (2.4 inches)	67%	very high
October Weather	14°C (57°F)	81 mm (3.2 inches)	72%	high
November Weather	7°C (45°F)	24 mm (0.9 inches)	80%	moderate
December Weather	3°C (37°F)	32 mm (1.3 inches)	83%	moderate