length of days Denver has not gone below 0f(-18c)

Denver usually goes below zero F (-18c) at least once every winter. In the mid 1940s there was a period of almost 4 years when Denver didn't go below 0F (-18C).   It ended on Feb 28, 1947.

Liek wise thee was a similar streak of almost 2 years in the mid 1920s, the very late 1990s-2000 and 1934 and 1935 ( the dust bowl years).