The average spring has warmed up 2.5 degrees in Philly. That’s not good for cherry blossoms.

Vince Marrocco, director of horticulture at Morris Arboretum & Gardens in Philadelphia, calls this one of the “weirder springs that I can remember.”

And that weirdness, which came with recent unseasonable warmth, has blossoms of some species of cherry trees peaking early at the arboretum.

“They’re at the peak of their bloom and others are going to be in peak bloom in a couple of weeks,” Marrocco said Tuesday. “We’re predicting the peak cherry bloom to be around the end of March. It should be about the seventh or 10th of April … we’re a good 10 days well ahead of where we ought to be.”

Although a cold spell is forecast for the days ahead, which may cause the pink and white blooms to brown, the trees will survive.

» READ MORE: Spring arrives in Philly with a bloom-threatening freeze in the forecast

The arboretum’s blossoms are not an anomaly. Springs have gotten warmer in Philly, and that means some types of cherry trees around the region are popping earlier than normal.

An Inquirer analysis shows the average spring temperature has risen roughly 2.5 degrees the last 50 years, according to data collected by the National Weather Service at Philadelphia International Airport from 1974 through 2023. That’s in line with weather data analyzed by Climate Central, a Princeton-based research nonprofit run by scientists and communicators.

It’s too early to know how this spring will stack up against others. Meteorological spring, which is based on the calendar and used by meteorologists, began March 1 and continues through May. Astronomical spring, or the vernal equinox, began Tuesday when the day was divided into roughly 12 hours of daylight and 12 hours of darkness.

Until this week, high temperatures in March had been above normal every day, culminating last week when they reached the high 70s — nearly 20 degrees above normal. The winter, while not as warm as that in 2022-23, was relatively mild.

A mild winter and spring combined to help some buds pop early, Marrocco said. He noted a variety of factors other than warmth prompt trees to bloom, such as length of days and amount of precipitation. Species react differently to weather, he said.

» READ MORE: Your 2024 Philadelphia cherry blossom guide

Morris Arboretum & Gardens has about 60 species of cherry trees.

“They don’t all bloom at once,” Marrocco said. Other native trees, such as red maples, have bloomed right on time.

Marrocco notes that weather is variable, and springs are often marked by warm days, followed by cold, as is happening this week.

But weather is separate from climate, which is measured over time. Data suggest there has been a change in spring over the decades. Washington, D.C.’s famed cherry blossoms this week hit their second-earliest peak bloom in more than a century of records.

Climate Central analyzed temperatures for 239 locations across the U.S. since 1970. Of those, 229 saw a rise in average spring temperatures of 2.2°F. The remainder saw some drop or no change for meteorological spring — March, April and May.

The Southwest has seen the biggest warm-up with Reno, Nev.; El Paso, Texas; Las Vegas, and Tucson, Ariz., all with rises of 6 degrees or more from 1970 to 2023.

“Over the long term, there definitely is a long trend toward warmer temperatures earlier in the year,” said Theresa Crimmins, director of the USA National Phenology Network based at the University of Arizona. “And we see plant and animal response, which takes the form of earlier activity, than we have seen in decades past.”

Phenology refers to the timing of natural cycles for plants and animals. The USA National Phenology Network analyzes data across the country to provide phenological data for those who need it to make forecasts or decisions, such as farmers.

Each year it tracks the start of spring through leaf out, which is the emergence of the first leaves of early plants such as lilacs. Philadelphia saw its earliest leaf out on record last year. That was largely because February 2023 averaged 42.7 degrees, second warmest on record for Philly dating back to 1875, according to the National Weather Service.

This year, Crimmins said, leaf out is not as early in the region. However, she said leaf out is still occurring about 10 days earlier than normal.

“Philadelphia is ahead of schedule, but not exceedingly so,” Crimmins said.

Data supplied by the Phenology Network show the number of days with temperatures favorable to growing plants in the region were above normal from January to March this winter and last. Warmer, longer seasons give plants more days to grow.

Jason Parker, district manager of the North Philadelphia office of the Davey Tree Expert Co., said he’s noticed the warmer springs because of his duties as an arborist. The growing season, he said, used to be about nine months but has expanded to 10 or more. He also says cherry blooms are running about 10 days ahead of normal.

“There’s definitely something to that climate change,” he said.

Parker explained that the warm weather early on that prompts flowers to bloom ahead of their typical schedule can be damaging when frosts abruptly arrive, such as is expected this weekend. While freezing temperatures might cause flowers to fall, it stresses trees by forcing them to produce more leaves, draining energy. Weakened trees are more susceptible to such pests as the Japanese beetle, he said.

“It start things off in a bad way for the tree,” Parker said.