September weather forecast
Jacksonville, FL

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Water geysers at the fountain of Jacksonville in Florida, USA, with the cityscape
Water geysers at the fountain of Jacksonville in Florida, USA, with the cityscape

Weather in September

As September comes around, Jacksonville experiences a gradual transition from summer towards fall. There is a noticeable drop in the sea temperature from 83.5°F (28.6°C) in August to 82.9°F (28.3°C). Despite the transition period, the vibrancy of Jacksonville's weather persists. The daylight hours gradually reduce, simplifying the shift towards the cozier latter months of the year. Nevertheless, the temperatures and relative humidity remain considerably high, still echoing summer resonance.

Temperature

The commencement of September in Jacksonville brings an average high-temperature of a still tropical 86.9°F (30.5°C), marking an inconsequential divergence from August. During September, Jacksonville experiences an average low-temperature of 73.8°F (23.2°C) at night.

Heat index

The heat index value for September is calculated to be a torrid 100.4°F (38°C). Adopt extra safety steps, risk of heat exhaustion and heat cramps is notable. Sustained activity might cause heatstroke.
Consider that heat index readings are for situations in the shade and light wind. The heat index may experience an enhancement of 15 Fahrenheit (8 Celsius) degrees under direct sunlight.
Note: The heat index, also known as 'feels like' or 'felt air temperature', quantifies the warmth felt when relative humidity is considered. An individual's temperature experience can be influenced by extra factors, including metabolic differences, activity levels, and clothing. Exposure to direct sun rays can influence the heat you feel, pushing the heat index up by 15 Fahrenheit (8 Celsius) degrees. Heat index values are primarily vital for children. Children often miss understanding the importance of rest and rehydration. Thirst usually appears late during dehydration - therefore, maintaining hydration, particularly during long physical activities, is essential.
Perspiration is the human body's physiological response to high temperatures and is an attempt to lower body temperature through evaporation of sweat. Elevated relative humidity disrupts typical body cooling by reducing the evaporation rate, consequently decreasing the body's cooling rate and enhancing the feeling of heat. Rising body temperatures resulting from an imbalance in heat absorption can lead to potential thermal issues.

Humidity

The average relative humidity in September is 75%.

Rainfall

In Jacksonville, in September, it is raining for 18.5 days, with typically 2.48" (63mm) of accumulated precipitation. In Jacksonville, Florida, during the entire year, the rain falls for 172.6 days and collects up to 25.35" (644mm) of precipitation.

Snowfall

In Jacksonville, snow does not fall in January through November.

Ocean temperature

In Jacksonville, in September, the average water temperature is 82.9°F (28.3°C).
Note: Ideal surface water temperatures for any water activity fall between 77°F (25°C) and 84.2°F (29°C), offering maximum enjoyment for lengthened periods.

Daylight

The average length of the day in September in Jacksonville is 12h and 20min.
On the first day of September in Jacksonville, sunrise is at 7:03 am and sunset at 7:49 pm. On the last day of the month, sunrise is at 7:19 am and sunset at 7:12 pm EDT.

Sunshine

In September, the average sunshine in Jacksonville is 8.5h.

UV index

In September, the average daily maximum UV index is 6. A UV Index reading of 6 to 7 represents a high health hazard from unprotected exposure to Sun's UV rays for ordinary individuals.
Note: The maximum UV index, 6 during September, leads to the following recommendations:
Inhibit overexposure. Warding off sun damage is of utmost importance. UV radiation from the Sun is most intense between 10 a.m. and 4 p.m. Try to avoid direct sunlight during this period. Stay sun-safe with clothing that is both closely woven and worn loosely. Stay alert! Reflective properties of sand and water amplify the Sun's UV radiation.
Updated: Feb 10, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

How hot is it in Jacksonville in September?

In Jacksonville, in September, the average high-temperature is 86.9°F (30.5°C), and the average low-temperature is 73.8°F (23.2°C). In September, the average heat index (a.k.a. 'feels like', 'felt air temperature'), which combines air temperature and relative humidity, is calculated to be 100.4°F (38°C).

What is the average humidity in September in Jacksonville?

In September, the average relative humidity in Jacksonville is 75%.

How many days does it rain in September in Jacksonville?

In Jacksonville, Florida, during September, the rain falls for 18.5 days and regularly aggregates up to 2.48" (63mm) of precipitation.

When it does not snow in Jacksonville?

January through November are months without snowfall in Jacksonville, Florida.

How warm is the water in September in Jacksonville?

In Jacksonville, Florida, the average seawater temperature in September is 82.9°F (28.3°C). Water temperature between 77°F (25°C) and 84.2°F (29°C) is regarded as very warm and enjoyable by all. With these temperatures, water activities are pleasurable, without feeling uncomfortable for prolonged periods.

What is the average length of the day in September in Jacksonville?

In Jacksonville, the average day length in September is 12h and 20min.

What time are sunrise and sunset in September in Jacksonville?

In September, on the first day of the month, sunrise is at 7:03 am and sunset at 7:49 pm. On the last day of the month, in Jacksonville, sunrise is at 7:19 am and sunset at 7:12 pm EDT.

How many hours of sunshine does Jacksonville have in September?

The average sunshine duration in September is 8.5h.

What is the UV index intensity in September in Jacksonville?

The average daily maximum UV index in September is 6. A UV Index value of 6 to 7 symbolizes a high health threat from unsafe exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Jacksonville, FL

Average temperature in September - Jacksonville, FL
  • Average high temperature in September: 86.9°F

The warmest months (with the highest average high temperature) are July and August (91.4°F).
The month with the lowest average high temperature is January (63.1°F).

  • Average low temperature in September: 73.8°F

The month with the highest average low temperature is August (76.6°F).
The coldest month (with the lowest average low temperature) is January (47.8°F).

Average pressure in September
Jacksonville, FL

Average pressure in September - Jacksonville, FL
  • Average pressure in September: 29.98"Hg

The month with the highest atmospheric pressure is January (30.14"Hg).
The months with the lowest atmospheric pressure are June, August and September (29.98"Hg).

Average wind speed in September
Jacksonville, FL

Average wind speed in September - Jacksonville, FL
  • Average wind speed in September: 5.7mph

The windiest month (with the highest average wind speed) is April (6.8mph).
The calmest months (with the lowest average wind speed) are July and August (5.2mph).

Average humidity in September
Jacksonville, FL

Average humidity in September - Jacksonville, FL
  • Average humidity in September: 75%

The month with the highest relative humidity is December (76%).
The month with the lowest relative humidity is March (69%).

Average rainfall in September
Jacksonville, FL

Average rainfall in September - Jacksonville, FL
  • Average rainfall in September: 2.48"

The wettest month (with the highest rainfall) is August (3.66").
The driest month (with the least rainfall) is January (1.1").

Average rainfall days in September
Jacksonville, FL

Average rainfall days in September - Jacksonville, FL
  • Average rainfall days in September: 18.5 days

The month with the highest number of rainy days is August (23.3 days).
The month with the least rainy days is November (9 days).

Average snowfall days in September
Jacksonville, FL

Average snowfall days in September - Jacksonville, FL
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is December (0.1 days).
The months with the least snowfall days are January, February, March, April, May, June, July, August, September, October and November (0 days).

Average sea temperature in September
Jacksonville, FL

Average sea temperature in September - Jacksonville, FL
  • Average sea temperature in September: 82.9°F

The best month for swimming (with the highest average sea temperature) is August (83.5°F).
The coldest month (with the lowest average sea temperature) is February (60.4°F).

Average daylight in September /
Average sunshine in September
Jacksonville, FL

Average daylight in September / Average sunshine in September - Jacksonville, FL
  • Average daylight in September: 12h and 2min

The month with the longest days is June (Average daylight: 14h and 6min).
The month with the shortest days is December (Average daylight: 10h and 12min).

  • Average sunshine in September: 8h and 3min

The month with the most sunshine is July (Average sunshine: 10h and 54min).
The month with the least sunshine is December (Average sunshine: 5h and 54min).

Average sunshine days in September
Jacksonville, FL

Average sunshine days in September - Jacksonville, FL
  • Average sunshine days in September: 8.7 days

The month with the most sunshine days is January (18.8 days).
The month with the least sunshine days is August (6.3 days).

Average UV index in September
Jacksonville, FL

Average UV index in September - Jacksonville, FL
  • Average UV index in September: 6

The months with the highest UV index are May, June, July and August (UV index 7).
The month with the lowest UV index is January (UV index 4).

Average cloud cover in September
Jacksonville, FL

Average cloud cover in September - Jacksonville, FL
  • Average cloud cover in September: 32

The month with the most cloud cover is December (Cloud cover 39).
The month with the least cloud cover is May (Cloud cover 27).

Average visibility in September
Jacksonville, FL

Average visibility in September - Jacksonville, FL
  • Average visibility in September: 6mi

The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

Jacksonville, Florida, USA

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