Boise’s 2015 weather: A year notable for its warmth, extended growing season ends with cold spell

Baby, it was warm outside.

Not today, of course, or this week. And it’s not going to feel warm anytime soon — we will have one of the coldest days of the year Sunday.

But overall, it was a notably warm year for Boise, according to National Weather Service data.

The annual average high temperature (through Dec. 23) was 66.8, which is tied with 1934 for the third-warmest on record, according to meteorologist Dave Groenert. That’s almost 4 degrees above normal.

The average low for the year was 44.6 degrees, about 5 degrees above normal. That’s on track to be the warmest on record, but it will depend on how the final days of the year play out.

It was a memorable year for farmers and gardeners. The last freeze of spring was a couple weeks early, and the first freeze of fall came several weeks late. The normal growing season is 159 days, and this year we got 201 days.

“We got an extra 42 days. This ended up being our second-longest growing season on record,” Groenert said, noting that this phenomenon wasn’t limited to the Boise area or even Idaho. “I have relatives back east in Virginia, and they were harvesting tomatoes in late November.”

The East Coast is having a warm, nonwhite Christmas. Temperatures in some places were 30 to 40 degrees above normal for Christmas Eve, according to The Washington Post. New York City’s high temperature Thursday was 72 degrees in Central Park, easily clearing the previous record of 56, set in 1988, according to Intellicast. In Norfolk, Va., Christmas Day came within a degree of 80, according to the National Weather Service. That’s compared to a Christmas Day average of 50 degrees. It was in the 60s in Boston and the 70s in Charlotte.

“The warmth is indirectly linked to the very strong El Nino event in which heat from abnormally warm waters in the tropical Pacific is infused into weather patterns over North America,” The Post reported. “In this case, the flow of air around high pressure centered over Bermuda is pumping deep tropical air straight up the East Coast.”

MILD WINTER, HOT SUMMER

Meteorological winter is December through February. Last winter was the third mildest on record, behind only 1917-18 and 1933-34.

About 6 inches of snow fell from last December to February, less than the 7.6 inches that fell in November 2014 alone. The first measurable snow this year was Nov. 15, when almost a half-inch was recorded at the airport.

Every month of 2015 except November was warmer than normal, and June was the warmest since record keeping began in 1869. The average temperature in June was 75.9, close to the norm for July, according to a Weather Service monthly summary.

In early December, there were six days with highs in the 50s.

DRY SPRING, WET FALL

Boise typically gets about 12 inches of precipitation each year. The city might fall a little short of that, in part because March and April showers didn’t materialize in any significant way.

There were 10 days of measurable precipitation during those two months, and precipitation totals were about an inch and a half lower than normal for that period.

Summer was typical, and fall was wetter than normal. A little more than 3 inches of precipitation was recorded from September through November — about an inch more than normal.

It’s been a snowy week, but not a snowy year. Through Dec. 23, just 8 inches had been recorded at the airport. That’s the 11th lowest amount in more than a century of data.

This story was originally published December 25, 2015 at 6:35 PM with the headline "Boise’s 2015 weather: A year notable for its warmth, extended growing season ends with cold spell."