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Growing seasons are longer in the United States than they used to be -- 10 days longer in the Northeast, according to a 2012 EPA report

(Environmental Protection Agency)

Syracuse, N.Y. -- The growing season in the Northeast has increased by 10 days in the past three decades, according to the federal Environmental Protection Agency.

But Syracuse's growing season actually got a bit shorter. Why?

Meteorologists and climatologists say they're not sure. It could be a function of Syracuse's location between the Great Lakes and the Appalachian range. It could be the way things have been measured and calculated.

The growing season, also known as the frost-free season, is defined as the number of days between the last freezing temperature of the spring and the first freezing temperature in the fall.

The EPA says the growing season is, well, growing across the United States. The biggest change is in the West, where the growing season is 16 to 19 days longer than it used to be. In the Northeast, it's 10 days longer. (See map above.)

The EPA compared the years 1991 to 2012 to a base period of 1901-1960. The report concluded that growing seasons were getting longer because of global climate change.

Syracuse showed little change during those two periods, however. In fact, the growing season was slightly shorter. From 1903 to 1960, the average growing season was 170 days. From 1991 to 2012, it was 168 days.

Those numbers don't include the past two years -- including 2014's record-breaking growing season of 207 days. If those years were included, the season average since 1991 would be 170 days.

NewsChannel 9 meteorologist Dave Eichorn said Syracuse's geography might explain why the growing season has remained relatively constant.

"Our proximity to the Great Lakes might have a stabilizing influence on our climate," Eichorn said. "While inland areas may warm more quickly earlier in the year, it might not be as noticeable if you're near a cold body of water."

Syracuse also sits just north of a range of hills that stretch from Pennsylvania to the Catskills, said Eichorn, who also teaches meteorology at SUNY College of Environmental Science and Forestry.

"We're in kind of a pit where cold air is a little bit slower to let go," he said. "We may be sort of a slower response area compared to other places that can respond to a change in climate more readily."

Climatologist Samantha Borisoff, with the Northeast Regional Climate Center, also said the Great Lakes influence might be a factor in the steady growing season. She said the measurement and calculations could be part of the explanation, too, and cautioned that it's difficult to draw conclusions about climate by looking at just one site.

"The 10 days is an average for the entire (Northeast)," Borisoff said in an email. "Some sites will be above that number (such as Central Park, which has seen an increase of about 15 days), while some sites, like Syracuse, will be below that number."

While the growing season isn't getting any longer, Syracuse has seen warmer days happening earlier in the year. The first occurrence of 60-degree, 70-degree and 80-degree days are coming earlier in the year than they used to.

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