07/08/2022
Following up on the last post- it turns out that a very useful measure of whether the lake is having a cold or warm year is to determine the date on which the lake surface temperature reaches 4C, or about 39F (when this happens depends on where you are in the lake- shallow water reaches this date earlier than deep water). This is the date when the lake can start to form a warm upper layer- sort of the beginning of "summer" for the lake. Comparing the last 41 years shows that there is a noisy but significant trend towards earlier onset of summer- about 3 days earlier every decade, which is a consequence of warmer winters. The red dot is UMDBuoy's estimate for this year- we're still a week or two away! Note 2014- the polar vortex winter, had a late onset, and 2012 (after a very warm winter) had very early onset. Last winter was fairly chilly, so this year's onset is relatively late.