Fall colors near peak, Indian summer ahead?

The elusive annual fall color peak is sweeping across Minnesota.

Northern Minnesota is already past peak color according to the latest update form the Minnesota Department of Natural Resources.

Fall color "peak" is a bit subjective. What's your favorite level of color? Do you still like some green mixed in? For most leaf peepers, this weekend could be the best fall color weekend for the Twin Cities and southern Minnesota.

Forecast: status quo for now

What you see is what you get the next few days across Minnesota. The responsible party?  A cool dry Canadian high pressure cell drifting overhead through Friday.

Watch the cool big blue "H" sag slowly south from Manitoba into Minnesota.

Here's a closer, more detailed look at forecast trends. Clear skies and a cool air mass at night should produce temps near or just above the 32-degree mark in the inner metro core Friday and Saturday morning. Will we see the first official 32 degree temperature at Minneapolis-St. Paul International Airport?

Place your bets.

Indian summer on the horizon?

We hear the term Indian Summer thrown about this time of year. What does it really mean? Is there an actual definition?

It turns out there is. Here's the American Meteorological Society's (AMS) definition of Indian summer from the Glossary of the AMS.

A period, in mid- or late autumn, of abnormally warm weather, generally clear skies, sunny but hazy days, and cool nights.

In New England, at least one killing frost and preferably a substantial period of normally cool weather must precede this warm spell in order for it to be considered a true "Indian summer."

It does not occur every year, and in some years there may be two or three Indian summers. The term is most often heard in the northeastern United States, but its usage extends throughout English- speaking countries. It dates back at least to 1778, but its origin is not certain; the most probable suggestions relate it to the way that the American Indians availed themselves of this extra opportunity to increase their winter stores.

The comparable period in Europe is termed the Old Wives' summer, and, poetically, may be referred to as halcyon days. In England, dependent upon dates of occurrence, such a period may be called St. Martin's summer, St. Luke's summer, and formerly All-hallown summer.

From this definition there are two true tests to be met before we can call a fall warm up "Indian summer."

1.) A period, in mid- or late autumn. Since meteorological fall runs from September 1 through November 30th we should at least be talking about dates after October 10th. 2.) Killing frost. At least one killing frost and preferably a substantial period of normally cool weather must precede this warm spell in order for it to be considered a true "Indian summer."  Much but not all of Minnesota has seen a killing frost so far. That may change this weekend as another shot of near freezing air nips at the inner metro core. We should be able to call any big warm up late next week a true "Indian Summer" in most of Minnesota. My feeling is that temps at least 10 degrees warmer than average would qualify for Indian summer this time of year. By next weekend the average metro high is 57 degrees. A warm up into the upper 60s to near 70 degrees qualifies fin my book. Red on the weather maps? Well, at least orange. Next week features more red than blue on the weather maps over the Upper Midwest. Here's the take of the National Oceanic and Atmospheric Administration's Climate Prediction Center on temperatures next week. Chances favor above average temps over most of the United States as the jet lifts north into Canada.

The detailed outlook for the Twin Cities from the from the European Centre for Medium-Range Weather Forecasts model agrees. Upper 60s by late next week? From the trends I'm seeing I wouldn't rule out another 70-degree day or two late next week into the weekend of Oct. 18.

Time for one more boat ride, bike ride or sunset at the beach? Keep the shorts handy just in case.