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
The onset of September introduces a moderate change in Darby's weather, with average high-temperatures falling from August's warm 76.3°F (24.6°C) to an enjoyable 66.2°F (19°C). Darby registers a significant drop in temperature in September, with average nighttime lows of 39.9°F (4.4°C).Humidity
In September, the average relative humidity is 57%.Rainfall
In Darby, in September, it is raining for 9.9 days, with typically 0.98" (25mm) of accumulated precipitation. In Darby, during the entire year, the rain falls for 163.6 days and collects up to 20.83" (529mm) of precipitation.Snowfall
Months with snowfall are January through May, September through December. September is the first month it typically snows. Throughout September, in the average 0.4 snowfall days, it receives 0.55" (14mm) of snow. Throughout the year, in Darby, there are 101.1 snowfall days, and 59.17" (1503mm) of snow is accumulated.Daylight
The average length of the day in September is 12h and 31min.On the first day of September, sunrise is at 6:58 am and sunset at 8:14 pm. On the last day of the month, sunrise is at 7:34 am and sunset at 7:17 pm MDT.
Sunshine
In Darby, Montana, the average sunshine in September is 9.5h.UV index
In September, the average daily maximum UV index is 3. A UV Index of 3 to 5 symbolizes a moderate threat to health from exposure to the Sun's UV radiation for the ordinary person.Note: A daily high UV index of 3 in September leads to these guidelines:
Ensure safety - Imperative it is to shield skin and eyes from damage. Stay safe from the Sun's strongest UV rays by limiting exposure during midday. A wide-brimmed hat is a shield, deflecting up to 50% of harmful UV radiation from eyes. Notice! The UV radiation of the Sun can be intensified nearly twofold due to the reflective quality of snow.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are September temperatures?
What is the average humidity in September?
How many days does it rain in September?
When does it start to snow?
What is the average length of the day in September?
When is the sunrise / sunset in September?
How long on average sun shines in September?
How high is the UV index in September?
Average temperature in September
Darby, MT
- Average high temperature in September: 66.2°F
The warmest month (with the highest average high temperature) is July (77°F).
The month with the lowest average high temperature is December (26.8°F).
- Average low temperature in September: 39.9°F
The month with the highest average low temperature is August (46.9°F).
The coldest month (with the lowest average low temperature) is December (14°F).
Average pressure in September
Darby, MT
- Average pressure in September: 29.99"Hg
The month with the highest atmospheric pressure is January (30.21"Hg).
The month with the lowest atmospheric pressure is June (29.93"Hg).
Average wind speed in September
Darby, MT
- Average wind speed in September: 4.4mph
The windiest month (with the highest average wind speed) is January (5.3mph).
The calmest month (with the lowest average wind speed) is August (4.1mph).
Average humidity in September
Darby, MT
- Average humidity in September: 57%
The month with the highest relative humidity is January (89%).
The month with the lowest relative humidity is August (50%).
Average rainfall in September
Darby, MT
- Average rainfall in September: 0.98"
The wettest months (with the highest rainfall) are February and April (2.36").
The driest month (with the least rainfall) is August (0.75").
Average rainfall days in September
Darby, MT
- Average rainfall days in September: 9.9 days
The month with the highest number of rainy days is May (19.5 days).
The month with the least rainy days is July (8 days).
Average snowfall in September
Darby, MT
- Average snowfall in September: 0.55"
The month with the highest snowfall is February (13.03").
The months with the least snowfall are June, July and August (0").
Average snowfall days in September
Darby, MT
- Average snowfall days in September: 0.4 days
The month with the highest number of snowfall days is February (19.3 days).
The months with the least snowfall days are June, July and August (0 days).
Average daylight in September /
Average sunshine in September
Darby, MT
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 42min).
The month with the shortest days is December (Average daylight: 8h and 42min).
- Average sunshine in September: 9h and 3min
The months with the most sunshine are July and August (Average sunshine: 11h and 42min).
The months with the least sunshine are January and December (Average sunshine: 5h and 24min).
Average sunshine days in September
Darby, MT
- Average sunshine days in September: 16.1 days
The month with the most sunshine days is July (18.9 days).
The month with the least sunshine days is February (5.6 days).
Average UV index in September
Darby, MT
- Average UV index in September: 3
The month with the highest UV index is July (UV index 5).
The months with the lowest UV index are February and December (UV index 1).
Average cloud cover in September
Darby, MT
- Average cloud cover in September: 21
The month with the most cloud cover is February (Cloud cover 51).
The month with the least cloud cover is August (Cloud cover 13).
Average visibility in September
Darby, MT
- Average visibility in September: 6mi
The months with the highest visibility are May, June, July, August, September and October (6mi).
The months with the lowest visibility are January, February, March and December (4mi).
Darby, Montana, USA
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