September Weather in Saint John, United States

Last updated: June 24, 2025

In September, the average temperature in Saint John, United States hovers around 18°C (64°F). Temperatures can vary significantly, with a minimum of 3°C (37°F) and a maximum reaching up to 36°C (96°F). This month sees an average precipitation of 22 mm (0.9 in) spread over just 4 days, coupled with an average humidity level of 60%. This combination of factors creates a unique climate experience for visitors and locals alike.

September Temperature in Saint John

In September in Saint John, the average temperature is 18°C (64°F). Maximums can reach 36°C (96°F) and minimums can be as low as 3°C (37°F). Be prepared for a range of temperatures, making it essential to pack both light clothing for the warmth and warmer layers for the cooler nights.

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 18°C (64°F), with highs reaching up to 36°C (96°F) and lows dropping to around 3°C (37°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 precipitation amount is 22 mm (0.9 in) over a duration of 4 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 22 mm (0.9 inches) of precipitation spread over approximately 4 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 60%. With an average temperature of 18°C (64°F), this humidity feels like a gentle and refreshing embrace, making it perfect for leisurely strolls and sightseeing.

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 60%, 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 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 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 7, which falls under the 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	1°C (35°F)	62 mm (2.5 inches)	85%	low
February Weather	1°C (34°F)	74 mm (2.9 inches)	86%	moderate
March Weather	6°C (42°F)	56 mm (2.2 inches)	86%	moderate
April Weather	10°C (50°F)	48 mm (1.9 inches)	82%	high
May Weather	15°C (59°F)	45 mm (1.8 inches)	77%	very high
June Weather	20°C (68°F)	20 mm (0.8 inches)	79%	very high
July Weather	24°C (76°F)	2 mm (0.1 inches)	77%	very high
August Weather	24°C (75°F)	10 mm (0.4 inches)	62%	very high
September Weather	18°C (64°F)	22 mm (0.9 inches)	60%	high
October Weather	10°C (50°F)	54 mm (2.1 inches)	80%	moderate
November Weather	5°C (41°F)	74 mm (2.9 inches)	87%	moderate
December Weather	1°C (34°F)	70 mm (2.8 inches)	86%	low