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 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 a local and national spring leaf 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 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.”

Fox butterflies are already out in Massachusetts and New York. Beetles are scurrying around Martha’s Vineyard. Crocuses and snowdrops are in full flower in suburban Boston – all exceptionally early because of warm temperatures and little snow cover, said Boston University biology professor Richard Primack.

“I am already hearing woodpeckers knocking on tree trunks,” when these sounds usually occur in March or April, said Primack, editor of the journal Biological Conservation.

The northern shoveler duck is usually the next to last duck to make it to upstate New York, arriving sometime in April, but it’s already here, said Kevin McGowan, an ornithologist at the Cornell Lab of Ornithology.