Jeffers Foundation


Data from Freshwater Society Minnesota Weatherguide Environment Calendar and Almanac (Jim Gilbert for Phenology and Rod Nerdahl for Astronomy)


Phenology: Fourth Week of May

American robins begin singing around 4:30 am and continue until about 9:15 pm. White-tailed deer fawns - about seven pounds at birth - are arriving; twins are common. Farmers are harvesting the first crop of alfalfa hay in southern Minnesota. Heavy shade covers southern Minnesota and Wisconsin deciduous forests; in the northern parts of the states such trees as quaking aspens and sugar maples have tiny leaves.

View the May Phenology Information from the Freshwater Society Minnesota Weatherguide Environment Calendar and Almanac >>

Species of the Month

Eastern tiger swallowtail butterfly (Papilio glaucus)

Eastern tiger swallowtail butterfly (<em>Papilio glaucus</em>)
Nile Fellows

The Eastern tiger swallowtail is one of our most common and easily recognizable butterflies. They are bright yellow with black tiger stripes upon a four-inch wingspan, with an extended small tail on the bottom of each back wing. The first generation of these colorful butterflies emerges in May and a second brood in early August, when they again become a familiar sight for the remainder of the month. As caterpillars first hatch they resemble bird droppings, a great camouflage. The caterpillars eventually turn green and have bright eyespots that deter predators. Caterpillars feed on leaves of ash and wild cherry trees. The adult butterflies feed on nectar from a great variety of flowering plants.

Astronomy: May

May night sky and the coma cluster
May night sky and the coma cluster
Can you find the Big Dipper in this photo? It is centered just below the top edge. Follow the handle's curve to the left to pinpoint the brilliant star, Arcturus. Look to the right of Arcturus for a compact bunch of stars. It is the most obvious feature in the pint-sized spring constellation Coma Berenices. This bundle of stars is a star cluster, similar to the famous Seven Sisters star cluster visible on winter evenings. Follow the "arc to Arcturus" high in the southern sky to discover Coma Berenices and the Coma Cluster yourself!

Morning Stars

Mercury is too close to the Sun to see this month. Venus however, climbs out of the Sun's glare to appear between six and nine degrees above the eastern horizon one hour before sunrise. This will be Saturn's last month as a morning star. The famous ringed planet appears about 17 to 23 degrees above the south-southwestern horizon an hour before sunrise. Look for Saturn near the Moon on May 13.

Evening Stars

Mars gradually sinks into the Sun's glare, appearing 11 degrees above the west-southwestern horizon an hour after sunset on May 1. By month's end, Mars' elevation is a mere three degrees. Jupiter is a much easier target. Look for it between 32 and 41 degrees above the southsouthwestern horizon one hour before sunrise. The Moon passes Jupiter on May 7 and Mars on May 26.

Sun Declination

View the May Astronomy Information from the Freshwater Society Minnesota Weatherguide Environment Calendar and Almanac >>


First monarch butterfly arrives (Carver County):
2015 June 1
2014 May 21
2013 May 31
2012 May 2
2011 May 25




3rd, First Quarter Moon - 9:47 pm

5th, Eta Aquarid Meteor Shower peak - 8:54 pm

10th, Full Moon - 4:42 pm

12th, Moon apogee; 252,411 miles - 3:15 pm

18th, Last Quarter Moon - 7:33 pm

25th, New Moon Budding Plants (Ojibwe) - 2:44 pm

25th, Moon perigee; 221,970 miles - 8:20 pm

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