United StatesAverage weather for Boulder in September
It's warm in September in Boulder with an average temperature of 27°C. Temperatures this month range from a low of 21°C to a high of 31°C. At night, you can expect temperatures between 9°C and 16°C.
Start of September
The month of September starts in Boulder with hot temps, averaging around 29°C during the day and nights around 14°C. There’s little chance of precipitation. The weather’s mostly sunny and dry.
With the temperature difference between day and night, it’s smart to wear layers.
Mid September
By mid-September, daytime temps drop to around 28°C, with nights around 13°C. Not much precipitation expected during this period. It’s mostly dry and sunny.
Since it cools down at night, it’s a good idea to wear layers.
End of September
By the end of September, the average daytime temperature in Boulder is around 25°C, while nighttime temps are about 11°C. There’s hardly any chance of precipitation. The weather will be mostly dry with plenty of sun.
In September, there is an average of 14 mm of precipitation, spread over 3 days. Of the total precipitation, about 0,4 cm falls as snow in September. The wind speed is around 3 Bft, mostly coming from the South.
Boulder in September |
New York | ||
|---|---|---|---|
 Average temperature |
27°C | 27°C | |
 Max. temperature |
31°C | 31°C | |
| Min. temperature |
21°C | -5°C | |
 Total precipitation |
14 mm | 57 mm | |
| Rainy days |
3 days | 9 days | |
 Total snowfall |
0,4 cm | 0 cm | |
| Snowy days |
1 day | 0 days | |
August
UV index
The UV index is a maximum of 8 this month. That's a very high value on the intensity scale of 1 to 11. Unprotected skin can burn within 10-15 minutes.
Is September a good time to visit Boulder?
Looking for great weather? September is a good time to be in Boulder. The temperatures are nice, and there’s little chance of rain this month.
Temperature records
With 39°C in 2019, Boulder reached the highest temperature in September over the past 10 years. The lowest daytime temperature in this month was 6°C in 2020. The extreme nighttime temperatures ranged from a lowest recorded value of 0°C to a highest value of 22°C.
Check out the climate of Boulder for all months and discover the best travel time
Daily Temperature in September in Boulder
This chart shows the average daily high and low temperatures in September for Boulder, in degrees Celsius. The red line represents the highs, and the blue line shows the lows. The days of the month are displayed at the bottom of the chart. The data, based on historical observations, provide the average temperatures for this month.
Daily Precipitation in September in Boulder
The chart below shows the average daily precipitation in September for Boulder, measured in millimeters over the past few years. Precipitation is always measured as water, even if it’s snow or hail. The days of the month are listed at the bottom of the chart.
A low average precipitation means that the chance of rain on that day is usually small, while a higher average suggests that it rained more often. But remember, it’s just an average, and every day can be different. Based on historical weather data for September, you can expect about 3 days of precipitation in Boulder.
Daily Snowfall in September in Boulder
This chart shows the average daily snowfall in September in Boulder, measured in centimeters. The bottom of the chart shows the days of the month. The data is based on historical measurements and gives an idea of the average snowfall in September.
Daily UV index in September in Boulder
This chart shows the average daily UV index in September in Boulder, with the UV index ranging from 0 to a maximum of 11. The bottom of the chart shows the days of the month. Based on historical data, this chart provides an idea of the daily UV radiation levels you can expect.
Temperature in September in Boulder over the years
This chart shows the average temperature in September in Boulder, measured in degrees Celsius, over the past few years.
Total precipitation in September in Boulder over the years
This chart shows the average precipitation in September in Boulder, measured in millimeters over the past years. Precipitation is always measured as water, whether it’s snow or hail.
Snowfall in September in Boulder per year
This chart shows the average snowfall in September in Boulder, measured in centimeters, over the past few years.
Daily weather in September for Boulder
Click on any day in September to get detailed info about the usual weather on that day in Boulder. Check out the historical temperatures and precipitation over the past 10 years on this day.
Weather experiences in September in Boulder
Have you been to Boulder in September?
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Average weather in Boulder by month
Click on a month below to see detailed weather info for Boulder. Based on historical weather data, you can see the average temperature, precipitation, wind, and UV index for each day of the month.
