The ISK holds an annual competition to guess the official Ice Out date on Lake Minnetonka, I was interested in understanding what this actually meant so went digging through the DNR’s website and came across the page that shows the official Ice status for all the major Minnesota lakes. Quoting from the official site:
The definition of lake ice-out varies from lake to lake, and individual to
individual. For some, ice-out occurs only when the lake is completely free of
ice. For others, ice-out is defined as the moment when navigation is possible
from point A to point B. And yet for others, ice-out is when 90 percent of the
lake is ice free. Due to the variable definitions of this rather subjective
observation, the State Climatology Office attempts to contact the same
individuals each year to maintain a consistent record.
This seems rather vague and woolly to me, but I thought it worthwhile checking out the Lake Minnetonka data which comprises 131 years of readings, so clearly not the same observer, but none the less, the earliest Ice Out date on record in March 11th during 1878, and the latest was May 8th during 1856, the computed average of the past 131 years is April 13th – I think we are going to be early this year if the wonderful weather of the past two weeks continues – its in the sixties again today.