September Weather in Johnston, United States

Last updated: June 24, 2025

In September, the average temperature in Johnston, United States hovers around 25°C (77°F). Expect a wide range, with minimums dipping to 11°C (52°F) and maximums soaring to 37°C (99°F). Precipitation averages 84 mm (3.3 in) over 7 days, accompanied by a notably high humidity level of 83%. Prepare for a mix of warm days and the occasional shower!

September Temperature in Johnston

In September in Johnston, the average temperature is 25°C (77°F). Maximums can reach 37°C (99°F), and minimums can be as low as 11°C (52°F). This weather makes Johnston an ideal destination for travelers seeking warm and pleasant conditions.

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

The chart illustrates September temperature patterns in Johnston, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Johnston, September typically has an average temperature of 25°C (77°F), with highs reaching up to 37°C (99°F) and lows dropping to around 11°C (52°F).

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

September Precipitation in Johnston

In Johnston in September, the total precipitation amount is 84 mm (3.3 in) distributed over a span of 7 days.

September Precipitation Trends in Johnston

The chart displays monthly precipitation patterns in Johnston, 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 Johnston, September typically receives around 84 mm (3.3 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 Johnston

In Johnston in September humidity is 83%. With an average temperature of 25°C (77°F), this humidity feels like a warm, enveloping blanket, making it essential for travelers to stay hydrated and seek shade to enjoy their adventures comfortably.

September Average Humidity in Johnston

This chart illustrates the average monthly humidity levels in Johnston, 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 Johnston is approximately 83%, 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 Johnston

In Johnston 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 Johnston.

Maximum UV Index Levels in Johnston for September

The chart shows the monthly maximum UV Index (UVI) for Johnston 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 Johnston typically reaches 9, which falls under the very high exposure category.

Data source: Johnston 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 Johnston Compares to Other Months

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

This table compares monthly weather conditions in Johnston, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	9°C (48°F)	84 mm (3.3 inches)	86%	moderate
February Weather	12°C (54°F)	114 mm (4.5 inches)	81%	high
March Weather	14°C (58°F)	85 mm (3.4 inches)	81%	very high
April Weather	18°C (65°F)	115 mm (4.5 inches)	79%	very high
May Weather	23°C (74°F)	110 mm (4.3 inches)	75%	extreme
June Weather	26°C (79°F)	101 mm (4.0 inches)	75%	extreme
July Weather	28°C (82°F)	137 mm (5.4 inches)	80%	extreme
August Weather	27°C (80°F)	142 mm (5.6 inches)	81%	extreme
September Weather	25°C (77°F)	84 mm (3.3 inches)	83%	very high
October Weather	20°C (69°F)	80 mm (3.1 inches)	78%	very high
November Weather	13°C (55°F)	69 mm (2.7 inches)	85%	high
December Weather	10°C (51°F)	119 mm (4.7 inches)	87%	moderate