Daffodils bloom in New York's Central Park, Tuesday, Feb. 28, 2017. Crocuses, cherry trees, magnolia trees are blooming several weeks early because of an unusually warm February. Some climate experts say it looks like, because of an assist from global warming, spring has sprung what may be record early this year in about half the nation. (AP Photo/Mark Lennihan)
Daffodils bloom in New York's Central Park, Tuesday, Feb. 28, 2017. Crocuses, cherry trees, magnolia trees are blooming several weeks early because of an unusually warm February. Some climate experts say it looks like, because of an assist from global warming, spring has sprung what may be record early this year in about half the nation. (AP Photo/Mark Lennihan) Credit: Mark Lennihan

Washington — Spring has sprung early — potentially record early — in much of the United States, bringing celebrations of shorts weather mixed with unease about a climate gone askew.

Crocuses, tulips and other plants are popping up earlier than usual from Arizona to New Jersey and down to Florida. Washington is dotted with premature pink blossoming trees. Grackles, red-winged blackbirds and woodpeckers are just plain early birds this year.

The unseasonably warm weather has the natural world getting ahead of — even defying — the calendar, scientists said on Tuesday.

In cities like Indianapolis, Pittsburgh and Columbus, Ohio, spring has arrived about a month earlier than the 30-year average and about 20 days earlier than in 2012, which was the earliest spring on record.

Scientists at the U.S. Geological Survey’s National Phenology Network, which studies seasonal signs, have calculated local and a national spring index based on observations of lilacs, honeysuckles and temperature records that are fed into a computer model.

The spring leaf index goes back to 1900 and 2012 has been the earliest on record . But preliminary records show this year ahead of 2012 in a good chunk of the nation. It’s still too early to draw a conclusion for the country, said University of Wisconsin-Milwaukee scientist Mark D. Schwartz and Phenology Network Director Jake Weltzin.

As the world warms, spring is arriving earlier, but not everywhere. For a broad swath of the U.S., 2017 sticks out like a crocus in early February. Nashville, St. Louis, Washington, Atlanta, Pittsburgh, Columbus and Indianapolis are at least three weeks early on the spring index, but Phoenix and Los Angeles are running a bit late.

“It’s weird,” Weltzin said on Tuesday.

The latest early spring isn’t supposed to show up for decades based on computer simulations that model springs of the future, said Jeff Masters, meteorology director of the private Weather Underground.

“This is basically a year 2100 sort of spring that we’re seeing this year,” Masters said. “Way surprising.”