(CNN)Tucked among the thousands of iconic Yoshino cherry trees at the Tidal Basin in Washington, DC, is the "indicator tree," which erupts into full bloom as much as 10 days earlier than its neighbors and gives officials at the National Park Service a good idea when the rest of them might begin to flower.
This year the indicator tree already started budding — the first stage of the bloom cycle — in the middle of February. That can only mean one thing: Spring (and cherry blossom season) is coming early.
Experts said this year could be a record-breaking early bloom, as temperatures soar way above average for February. Over the past century, the historical average peak bloom date at the Tidal Basin has been April 4, but records show it's been coming earlier than usual in recent decades.
The earliest peak bloom on record was in March 15, 1990. Michael Litterst, communications chief for National Mall and Memorial Parks with the National Park Service, said he believes that date is "certainly in play this year."
"All indications are it's going to be earlier than average," Litterst told CNN. Last year's peak bloom was March 25. "We're about a month out from that, but given what we've seen so far, and given what the forecast is, I think we're probably looking at something earlier than that."
Peak bloom varies each year depending on weather conditions. According to the National Park Service, Yoshino trees usually reach peak bloom between the last week of March and the first week of April. And the blooming period itself could last several days — it all depends on the weather.
But with the rise of planet-warming pollution, temperatures are getting warmer. And warm winters cause plants and trees to blossom early. Several Japanese plum trees, for instance, which are usually the earliest flowering trees, already blossomed around the National Mall in late January.
"Heat is what partially drives trees like that to blossom," Litterst said. "And when you look at how mild this winter has been, and the fact that we've had zero snow or frozen precipitation this year, it's not a surprise that we're seeing this."
Litterst said he has noticed a connection between warmer temperatures and earlier peak bloom. For example, the average annual temperature at the Martin Luther King Memorial and around the Tidal Basin have "increased a statistically significant 2.5 degrees Fahrenheit between 1895 and 2017," he said.
At the same time that temperatures were warming, peak bloom dates have also been shifting early by approximately six days.
"And not surprisingly, we are seeing people who are coming in earlier in earlier" to see the capital's iconic cherry blossoms, he added.
It's not just Washington, DC. Spring leaf out — when the first tiny leaves emerge from buds of plants that are dormant in the winter — is already the earliest on record in parts of the Southeast, southern Midwest, and Mid-Atlantic, according to the National Phenology Network.
Even New York City is seeing spring leaf out 32 days earlier than normal.