WEATHER HISTORY 

Record High: September 1st, 1995, 88 degrees F.
Record Low: September 25th, 1970, 17 degrees F.

September has an average high of 72 degrees, and an average low of 40 degrees. Average precipitation is 1.78 inches.

ANIMAL HAPPENINGS

Migration for many animals is in full swing. Monarch butterflies are heading south to Mexico and many other insects are seeking protection right now from the on-coming cold - either by heading south or crawling into your home (box elder bugs and some spiders). Many birds are turning south or are passing through from the mountains to the north, all heading to Mexico or Central America. Hummingbirds leave around the first weeks of September; hawks and other raptors typically leave towards the end of the month.

Elk are beginning to think about migration (they do a vertical migration, dropping from 11,000 to 5-7,000 feet by late October). But what is really on their minds is mating. Bull elk will begin to bugle and gather cow elk in groups called harems. The bull will protect their group from other males, bugling and challenging any that get too close, and mating with the cows in early October. The best place to hear elk bugling is in the Animas Valley and in fields and meadows with thick forest cover nearby.

Elk were nearly eliminated from Colorado in the early 1900s because of heavy hunting. The Elk population was bolstered with transplants from the Yellowstone area and today the state elk herd numbers over 278,000. The Colorado Division of Wildlife is currently trying to decrease these numbers.

Young spiders begin “ballooning” to new areas this month. They do this by crawling up to the top of something near them (a blade of grass, fence post, shrub...) and releasing a single strand of silk into the air. After they have spun out several feet or more, the wind can catch the silk thread and carry the spider to new destinations. (Remember Charlotte's Web?)

Some ladybugs do something completely different - they fly up to the tops of high mountains and crawl under rocks to begin their dormant winter period. Some 70 species of ladybug are native to Colorado and about 10 to 12 non-native species have become established in Colorado during the past century.

PLANT HAPPENINGS

Wild
Leaves turn color. Aspen colors usually reach their peak by the fourth week in the high country. In the foothills, shrubs, leafy plants, and grasses start to change color. The last of the wild fruits ripen. Local apples reach their peak and Gambel Oak Acorns ripen.

http://www.durangonaturestudies.org/articles/101004.htm for more on Fall Leaves and http://www.durangonaturestudies.org/articles/091204.htm for more on Gambel Oaks.

Garden
We typically receive our first mild frost (down to 28 degrees) sometime in the first two weeks of September, and then experience an extended Indian Summer where days are warm and nights are cool.

If you keep warm season vegetables covered at night, you can usually milk them along until October. Now is the time to dry flour corn on the stalk and let winter squash and pumpkin skins harden up for winter storage. But be careful. A hard frost will turn your hard earned yields to mush.

Look for Winter Squash, Garlic, Pumpkin and the last of the summer warm season vegetables at local farmers markets.

ASTRONOMICAL HAPPENINGS 

CELESTIAL HAPPENINGS 

Use binoculars to view Uranus as it reaches opposition on the 5th. Bright light from the nearby Moon will make it difficult to see. Fading Venus sinks in the predawn east; Saturn, crossing into Leo, rises just ahead of morning twilight. The Moon will keep it company on the 18th. A partial lunar eclipse on the 7th can not be seen from North America. Jupiter alone remains in the evening sky, but it becomes quite low by month's end. On the 22nd, the Moon, at apogee, is at its farthest from the Earth for the year—248,000 miles. (Based on the Old Farmer's Almanac).

OTHER HAPPENINGS 

The first day of Fall, or the Fall equinox, occurs on September 23rdh. On this day, the sun rises exactly in the east, and sets exactly in the west, and everywhere on the planet experiences exactly 12 hours of daylight. From this day until the first day of winter on December 22nd, the sun will be rising slightly further south of east each day, and traveling slightly lower in the sky.