(The following snowfall data for Colorado Springs,Pueblo, and Alamosa has been compiled using NWS Pueblo and NCEI records)
(measurable snowfall defined as being greater than or equal to 0.1 inches)
Colorado Springs
Mean Date of First Snowfall………............October 19th
Earliest First Snowfall: Trace................................September 2nd, 1961
Earliest Measurable Snowfall: 4.2 inches.............September 3rd, 1961
Latest Measurable First Snowfall: 0.2 inches..........November 28th, 2010
Greatest Amount for First Snowfall: 6.0 inches....October 24th, 1997
(13.9 inches followed on October 25th, 1997. This was the Blizzard of '97)
Pueblo
Mean Date of First Snowfall………....…...........November 4th
Earliest First Snowfall: Trace....................................September 10th, 1898
Earliest First Measurable Snowfall: 7.3 inches.........September 17th, 1971
Latest First Measurable Snowfall: 1.4 inches..........December 10th, 1963
Greatest Amount for First Snowfall: 12.6 inches....October 31st, 1972
(4.9 inches followed on November 1st, 1972)
Alamosa
Mean Date of First Snowfall…..................……October 29th
Earliest First Measurable Snowfall: 4.2 inches..….September 3rd, 1961
Latest First Measurable Snowfall: 3.3 inches.....December 9th, 2012
Greatest Amount for First Snowfall: 13.1 inches.....October 30th, 1991
(2.0 inches followed on October 31st, 1991)
This website... https://www.climate.gov/news-features/blogs/beyond-data/first-dates
is a nationwide database of the historic date by which there's a 50% chance of at least 0.1" of snow on the ground.
It includes many more sites in southern Colorado.
The dates are earlier that those above because it deals in a percentage chance rather than the actual snowfall data.