Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average snowfall in September
- Average snowfall days in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
Entering September, the average high-temperature is recorded at a warm 84.7°F (29.3°C), exhibiting a minimal shift from August's 90.1°F (32.3°C). Johnston in September experiences a low-temperature average of 66.4°F (19.1°C).Heat index
The heat index for September is calculated to be a hot 93.2°F (34°C). Ensure additional precautions, heat exhaustion and heat cramps may be expected. Heatstroke could occur from sustained activity.Be informed that the heat index values are oriented around shady conditions and gentle breezes. The presence of direct sunlight can raise the heat index values by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like' or 'apparent temperature', is found by incorporating humidity levels into the air temperature measurement. One's perception of temperature is subjective, varying based on their activity and individual heat perception, influenced by factors like wind, clothing, and metabolic variations. With the sun shining directly, it's crucial to understand that it can increase the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly meaningful for babies and toddlers. Young individuals are generally in more danger than adults due to their lower capacity to sweat. Moreover, their large skin surface in relation to their small bodies and the increased heat generation from their activities makes them more vulnerable.
Humidity
In September, the average relative humidity is 71%.Rainfall
The month with the least rainfall is September, when the rain falls for 12.2 days and typically collects 1.42" (36mm) of precipitation.Snowfall
In Johnston, snow does not fall in April through November.Daylight
The average length of the day in September is 12h and 22min.On the first day of September, sunrise is at 7:01 am and sunset at 7:52 pm. On the last day of the month, sunrise is at 7:21 am and sunset at 7:12 pm EDT.
Sunshine
The average sunshine in September is 8.7h.UV index
The average daily maximum UV index in September is 6. A UV Index reading of 6 to 7 represents a high health hazard from unprotected exposure to Sun's UV rays for the ordinary person.Note: During September, 6 as the daily maximum UV index converts into the following advice:
Endorse precautions and be consistent with sun safety guidelines. Preventing sunburn is paramount. The Sun's UV radiation is most potent between 10 a.m. and 4 p.m. Try to limit direct exposure to the Sun during this period. Sunglasses providing both UVA and UVB protection are non-negotiable on sunlit days.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
How hot does it get in September?
What is the average humidity in September?
What is the driest month?
How many days does it rain in September?
When it does not snow?
How many hours of daylight does Johnston have in September?
When are sunrise and sunset in September?
How many hours of sunshine does Johnston have in September?
What is the UV index intensity in September?
Average temperature in September
Johnston, SC
- Average high temperature in September: 84.7°F
The warmest month (with the highest average high temperature) is July (91.4°F).
The month with the lowest average high temperature is January (52.7°F).
- Average low temperature in September: 66.4°F
The month with the highest average low temperature is July (72.5°F).
The coldest month (with the lowest average low temperature) is January (36.9°F).
Average pressure in September
Johnston, SC
- Average pressure in September: 30.02"Hg
The months with the highest atmospheric pressure are January, November and December (30.14"Hg).
The month with the lowest atmospheric pressure is June (29.98"Hg).
Average wind speed in September
Johnston, SC
- Average wind speed in September: 5.8mph
The windiest months (with the highest average wind speed) are February and April (8.1mph).
The calmest month (with the lowest average wind speed) is August (5.2mph).
Average humidity in September
Johnston, SC
- Average humidity in September: 71%
The month with the highest relative humidity is December (76%).
The month with the lowest relative humidity is July (70%).
Average rainfall in September
Johnston, SC
- Average rainfall in September: 1.42"
The wettest month (with the highest rainfall) is December (3.03").
The driest month (with the least rainfall) is September (1.42").
Average rainfall days in September
Johnston, SC
- Average rainfall days in September: 12.2 days
The month with the highest number of rainy days is July (17.5 days).
The month with the least rainy days is November (7.8 days).
Average snowfall in September
Johnston, SC
- Average snowfall in September: 0"
The month with the highest snowfall is February (0.59").
The months with the least snowfall are April, May, June, July, August, September, October and November (0").
Average snowfall days in September
Johnston, SC
- Average snowfall days in September: 0 days
The months with the highest number of snowfall days are January and February (0.4 days).
The months with the least snowfall days are April, May, June, July, August, September and October (0 days).
Average daylight in September /
Average sunshine in September
Johnston, SC
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 14h and 24min).
The month with the shortest days is December (Average daylight: 9h and 54min).
- Average sunshine in September: 8h and 4min
The months with the most sunshine are June and July (Average sunshine: 10h and 54min).
The month with the least sunshine is December (Average sunshine: 5h and 24min).
Average sunshine days in September
Johnston, SC
- Average sunshine days in September: 16.2 days
The month with the most sunshine days is October (21.8 days).
The month with the least sunshine days is July (11.2 days).
Average UV index in September
Johnston, SC
- Average UV index in September: 6
The months with the highest UV index are June, July and August (UV index 7).
The month with the lowest UV index is January (UV index 2).
Average cloud cover in September
Johnston, SC
- Average cloud cover in September: 30
The month with the most cloud cover is December (Cloud cover 41).
The month with the least cloud cover is October (Cloud cover 27).
Average visibility in September
Johnston, SC
- 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).
Johnston, South Carolina, USA
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