The observation site at the Dane County Regional Airport in Madison jumped ten degrees early Monday morning, and demonstrated how a warm lake can influence a nearby location. At 4 AM, the hourly observation showed a temperature of 34 degrees Fahrenheit. Just a bit before 5 AM CDT, the winds changed from calm, which prevailed overnight, to a southwest wind that was generally between 5 and 9 mph. Over the next two hours, the site experienced an increase in temperature, not generally seen in the surrounding areas, to 37 and 47 degrees at 5 and 6 AM, respectively. Lake Mendota, just southwest of the observation site, had a lake temperature in the upper 50s. The phenomenon seen and responsible for this rise in temperature is attributable to the nearby warm lake that provided localized heating to the downwind airport observation site. This effect can also be seen on the eastern side of Lake Michigan with two observations in the low 50s.
Below is an infrared satellite image at 4 AM showing the 34 degree obs at Madison. Note the infrared image’s warm "bulls-eye", signifying the warm temperatures of Lake Mendota and Lake Monona. Also of note, Lone Rock airport in the Wisconsin River Valley is at 29 degrees and there are two observations of 53 degrees on the east side of Lake Michigan (at Ludington, MI and Muskegon, MI).
Below is an infrared satellite image at 6 AM showing the 47 degree obs at Madison. Note the infrared image’s warm "bulls-eye", signifying the warm temperatures of Lake Mendota and Lake Monona. Notably, Lone Rock airport in the Wisconsin River Valley is at 27 degrees and the two observations on the east side of Lake Michigan (at Ludington, MI and Muskegon, MI) are at 53 and 54 degrees.
Below is a screenshot of the Madison, WI obs at the Dane Regional County Airport showing the hourly temperature reports.
Below is a screenshot of the NWS Mesonet showing the two obs downstream from Lake Mendota and Lake Monona at 45 and 47 degrees. Note the surrounding areas for the most part are in the 30s and low 40s.
Below is a map of the lake surface temperatures from satellite. However, this map shows the inland lake temperatures are in the 60s when the nearby lake of Lake Monona has been observed in the upper 50s the last two days. The Lake Monona observed lake temperature is likely more representative than the below map that was derived from temperatures over the last eight days.
Below is a Google satellite image showing the Dane County Regional Aiport (A) with respect to Lake Mendota.