Philly’s April hot spell has set records. But does it mean anything for the summer?

With records broken on back-to-back days, Philadelphia is experiencing one of its warmest April runs in the 150 years that the government has been keeping score officially.

After reaching a record high Wednesday, the temperature hit 91 at Philadelphia International Airport on Thursday afternoon, ousting the 90-degree reading on April 16, 2002, from the record books. In the morning, it didn’t get below 65, setting a record for the highest minimum for the date.

But coming after that memorable winter, April is about to prove it is a month for all seasons: Don’t be surprised to see frost and freeze warnings early next week.

“I mean, I don’t know how to dress,” said Ruth McDermott-Levy, codirector of the Mid-Atlantic Center for Children’s Health and the Environment at Villanova University. But, yes, she does see a bright side to the early heat burst: Consider it a sort of spring training for the inevitable summer heat to come.

And as for what April in July might mean for the actual summer, one veteran seasonal forecaster advises that what happens — or doesn’t — in the rain gauges may be more important than any early temperature trends.

One indication of the intensity of the warmth is the fact that Friday’s projected high in the low 80s would be normal for June but still would qualify as a cooldown. Saturday is expected to be several degrees cooler, and Sunday’s high could be as much as 30 degrees lower than Thursday’s.

It is hard to sustain a warm spell in April, said Tom Kines, a senior meteorologist with AccuWeather Inc., adding this is a prime period for so-called backdoor fronts. Instead of traveling northwest to southeast, they move northeast to southwest, importing chilly air from the ocean.

One of those is due to cross the region on Saturday, said Joseph DeSilva, a meteorologist at the National Weather Service office in Mount Holly, bringing a potent sea breeze with it.

As of Thursday morning, sea-surface temperatures in the nearby Atlantic Ocean were in the upper 40s to upper 50s, DeSilva said.

And gardeners beware: The chill will be more evident Monday morning, when the weather service might post frost advisories, with lows in the upper 30s, DeSilva said, and maybe even freeze warnings for parts of the region for Tuesday morning as temperatures tumble deeper into the 30s.

Before that happens, however, the grasses and the plants may get a decent watering on Sunday, perhaps as much as a half inch of rain, DeSilva said.

The rain totals may bear watching in the next several weeks, said Paul Pastelok, the prime seasonal forecaster with AccuWeather Inc.

“What can drive any heat the rest of spring and early summer is the dryness of the ground,” Pastelok said.

Dryness begets dryness as the sun can spend its energy heating the surface rather than using it to evaporate water.

Right now, Philly is having a virtual harvest of dryness. With its Thursday update, the U.S. Drought Monitor has the entire region in “moderate drought.” Philadelphia has had below-normal rainfall for seven consecutive months.

While “it’s tough” to go too long without rainfall around here, given the proximity of so much water, on occasion the region has encountered a run of “bad luck” in which systems show up dry or spend their rain somewhere else, AccuWeather’s Kines said.

“A lot of times there’s an opportunity, and it just doesn’t happen,” he said.

Probably nothing, Pastelok said.

“This current heat wave really does not give an indication to what the summer can be like,” he said. An Inquirer analysis of temperature records in past years with hot shots in April — on average 90-degree readings in April have occurred about once every seven years — shows no correlation with the summer to follow.

The warming of the tropical Pacific, a potential El Niño event, has not been a factor: Water temperatures out that way still are at or slightly below normal.

Another system in the western Pacific has altered patterns in such a way that the West has turned stormy, while the Northeast has been quite warm, Pastelok said.

“We do see changes coming,” he said. “There will be more frequent cooldowns, some warmth in between, for the last 10 days of April into early May.”

In the meantime, said McDermott-Levy, who has a particular interest in weather-body matters, the hot spell was a decent warmup for the heat almost certainly to come.

Summers in Philly have been trending warmer this century.

“Driving into work, I see all these workers out fixing the roads,” she said. “I want to scream, ‘Are you drinking enough water? Are you taking breaks from the heat?’

“We need to be prepared. This is only April. What’s going to happen in July?”