Today marks the 81st anniversary of the warmest air temperature ever recorded for the Twin Cities: It was 108 degrees on July 14, 1936.

I have told my students for years that air temperatures should be taken 6 feet off the ground, in the shade, but have just learned that worldwide standard measuring conditions for temperature are 4.9 feet above ground in the shade.

The highest temperature recorded in Minnesota? It happened July 29, 1917, when it was 114.5 degrees in the west-central city of Beardsley. (By the way, the listed world record is 134.1 degrees July 10, 1913, at Furnace Creek Ranch in Death Valley, Calif.)

When it really gets hot in Minnesota many of us think about jumping into one of the lakes. Lake surface temperatures of more than 80 degrees are not unusual during hot spells. Some people worry about American robins hunting on their lawns under the intense heat rays of the summer sun, panting with open bills. Birds have no sweat glands, so in the warm weather they get rid of excess body heat by panting. During the hottest part of the day, birds become less active and find shaded places where they pant and rest.

Jim Gilbert's Nature Notes are heard on WCCO Radio at 7:15 a.m. Sundays. His observations have been part of the Minnesota Weatherguide Environment Calendars since 1977. He taught and worked as a naturalist for 50 years.