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
Johnston, Iowa, in September undergoes a slight reduction in the average high-temperature, shifting from August's warm 81.3°F (27.4°C) to a still moderately hot 75.6°F (24.2°C). Throughout September nights, Johnston registers an average low-temperature of 55.9°F (13.3°C).Humidity
In September, the average relative humidity is 76%.Rainfall
In September, the rain falls for 9.7 days. Throughout September, 1.73" (44mm) of precipitation is accumulated. In Johnston, during the entire year, the rain falls for 114.6 days and collects up to 15.51" (394mm) of precipitation.Snowfall
June through September are months without snowfall.Daylight
In Johnston, the average length of the day in September is 12h and 28min.On the first day of the month, sunrise is at 6:41 am and sunset at 7:47 pm. On the last day of September, sunrise is at 7:11 am and sunset at 6:57 pm CDT.
Sunshine
In Johnston, the average sunshine in September is 9.4h.UV index
In September, the average daily maximum UV index is 4. A UV Index of 3 to 5 symbolizes a medium health hazard from exposure to the Sun's UV radiation for average individuals.Note: A daily high UV index of 4 in September leads to these guidelines:
Preventative actions are necessary - Suggestions to safeguard against sun damage are in order. Sun's radiation is most powerful around mid-day, so it's best to limit outdoor activities during this time. Equip yourself with UVA and UVB-filtering sunglasses on clear, sunny days.
Frequently asked questions
What are September temperatures in Johnston?
What is the average humidity in September in Johnston?
How much does it rain in Johnston in September?
When it does not snow in Johnston?
Does it snow in Johnston in September?
What is the average length of the day in September in Johnston?
When is the sunrise / sunset in September in Johnston?
How long on average sun shines in September in Johnston?
How high is the UV index in September in Johnston?
Average temperature in September
Johnston, IA
- Average high temperature in September: 75.6°F
The warmest month (with the highest average high temperature) is July (82.4°F).
The month with the lowest average high temperature is January (27.9°F).
- Average low temperature in September: 55.9°F
The month with the highest average low temperature is July (65.1°F).
The coldest month (with the lowest average low temperature) is January (14.4°F).
Average pressure in September
Johnston, IA
- Average pressure in September: 30.01"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.88"Hg).
Average wind speed in September
Johnston, IA
- Average wind speed in September: 8mph
The windiest month (with the highest average wind speed) is April (10.4mph).
The calmest months (with the lowest average wind speed) are July and August (7mph).
Average humidity in September
Johnston, IA
- Average humidity in September: 76%
The month with the highest relative humidity is January (83%).
The month with the lowest relative humidity is October (70%).
Average rainfall in September
Johnston, IA
- Average rainfall in September: 1.73"
The wettest months (with the highest rainfall) are May and June (2.52").
The driest month (with the least rainfall) is January (0.47").
Average rainfall days in September
Johnston, IA
- Average rainfall days in September: 9.7 days
The month with the highest number of rainy days is May (16.3 days).
The month with the least rainy days is February (3.5 days).
Average snowfall in September
Johnston, IA
- Average snowfall in September: 0"
The month with the highest snowfall is January (2.2").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Johnston, IA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (8.4 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Johnston, IA
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 12min).
The month with the shortest days is December (Average daylight: 9h and 12min).
- Average sunshine in September: 9h and 2min
The month with the most sunshine is July (Average sunshine: 10h and 24min).
The month with the least sunshine is January (Average sunshine: 4h and 18min).
Average sunshine days in September
Johnston, IA
- Average sunshine days in September: 17.8 days
The month with the most sunshine days is December (22.8 days).
The month with the least sunshine days is June (11.2 days).
Average UV index in September
Johnston, IA
- Average UV index in September: 4
The months with the highest UV index are June and July (UV index 6).
The month with the lowest UV index is January (UV index 1).
Average cloud cover in September
Johnston, IA
- Average cloud cover in September: 28
The month with the most cloud cover is January (Cloud cover 53).
The month with the least cloud cover is September (Cloud cover 28).
Average visibility in September
Johnston, IA
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, August, September, October, November and December (6mi).
The month with the lowest visibility is July (5mi).
Johnston, Iowa, USA
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