First Day of Snow in Boulder

Statistics from 1948-present

First day of measurable snow (greater than a trace) at the official Boulder weather station (currently NIST)

The latest known day is Nov 26 1910 (0.5). Older data can be problematic as not all days are available or are listed in the official record correctly. Measurement was often made just at 5pm so snow could have melted before a measurement was recorded. Data from 1948 onwards is more robust. 

	  
earliest day of 1st snow:  Sep 12 (1974)
latest day:                Nov 17 (2016)

average:                   Oct 17

low decile                 Sep 20
first quartile             Sep 30
median                     Oct 20
third quartile             Oct 30
high decile                Nov  9

standard deviation         18.6 days
plot of first day snow in Boulder

List first day of snow in Boulder 1948-present

1948   October   16
1949   October   19
1950   November   2 
1951   September 21
1952   October   14
1953   November   4 
1954   October   25
1955   October   23
1956   October   24
1957   October   25
1958   September 30
1959   September 29
1960   October   15
1961   October   29
1962   November  15
1963   October   31
1964   November  14
1965   September 20
1966   October   14
1967   October   29
1968   October    9
1969   October    3 
1970   September 25
1971   September 17
1972   October   30
1973   November   2 
1974   September 12
1975   October   23
1976   October   26
1977   November   8 
1978   October   23*
1979   October   29
1980   October   27
1981   October   25
1982   October   19
1983   November   8 
1984   September 25
1985   September 28
1986   October   11
1987   November  15
1988   November  15
1989     missing
1990   October    8 
1991   October    4 
1992   November   2 
1993   September 13
1994   September 21
1995   September 21
1996   September 26
1997   October   24
1998   November   7
1999   September 28
2000   September 23
2001   October    5
2002   October   23
2003   October   30
2004   November   1
2005   November  15
2006   October   10 (1am)
2007   October   21
2008   October   13
2009   October   10
2010   November   9
2011   October   26
2012   October    5
2013   October    4
2014   September 12
2015   November 11
2016   November 17
2017   October 5
2018   October 10
2019   October 10
2020   September 8
2021   November 17
2022   October 27
2023   October 28
2024   November 4

*1978: The data at PSL has it as Nov 26. However, it did snow several times before that date and some of the "0s" are not. Oct 23rd was the first date.