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Weather service has flip-flopped on water year start

Why don't you include September rainfall amounts in your "season to-date" totals? Seems idiotic for a news outlet!

— M.J.S., submitted online

Pinpointing the start of the water year should be easier than predicting the arrival of the next big storm, but both tasks can be tricky and require some local expertise. Fortunately, the Medford office of the National Weather Service is prepared with all the facts, figures and forecasts.

The friendly meteorologists there confirmed that the water year indeed starts Oct. 1 and ends Sept. 30. That's why the season-to-date totals don't include September.

The Medford office shifted to that schedule last year to be in line with the rest of the nation after years of using Sept. 1 as a start date. Old-timers say the Rogue Valley's rainy season used to start in September, so the water year started Sept. 1.

The water year is a measuring convention designed to combine cold, wet months in one 12-month cycle to keep track of water resources most efficiently. The National Weather Service, U.S. Geological Survey, and the Community Collaborative Rain, Hail and Snow Network, a nationwide group of volunteers who collect weather data, all use Oct. 1, recognizing that for most of the country hot weather has subsided by then and winter storms that bring cool weather and plenty of precipitation to replenish soil moisture are on the way.

Just to make things more confusing, the local office was using Oct. 1 as a start date until a few years ago. The last time the Since You Asked weather watchers tackled a question about the start of the water year in 2010, we declared that after years of ignoring local convention with a nationally set October start, the weather service here finally had switched to a September start for the water year. Maybe deciding when the water year starts is a little like figuring out which way the wind is blowing.

—Send questions to “Since You Asked,” Mail Tribune Newsroom, P.O. Box 1108, Medford, OR 97501; by fax to 541-776-4376; or by email to youasked@mailtribune.com. To see a collection of columns, go to mailtribune.com/youasked. We’re sorry, but the volume of questions received prevents us from answering all of them.