The Delaware River may look tempting during a hot Philly summer, but a new study emphasizes that swimmers are better off heading upstream.

Why it matters: Swimming in contaminated water can cause stomach illnesses, eye infections and skin rashes.

State of play: A recent report from the nonprofit PennEnvironment found potentially unsafe contamination levels along nearly all of Philly's stretch of the Delaware River.

• E. coli levels exceeded federal standards at 37 out of 43 testing locations on at least one day, per the analysis.
• Water quality was far better north of the city, including areas as close as Bucks County as well as farther up into the Poconos.

How it works: PennEnvironment analyzed federal E. coli monitoring data at more than 650 monitoring locations in Pennsylvania rivers, streams and lakes in 2024 and 2025.

What they found: Roughly 55% of sites statewide had potentially unsafe contamination levels on at least one day.

• That included other locations in the Philly region, including sections of French Creek, Brandywine Creek and Red Clay Creek.

Zoom in: Philly's stretch of Delaware River isn't so different from a giant toilet.

• 12.7 billion gallons of untreated sewage and polluted stormwater are estimated to flow into the river annually.

Plus: Other hazards for would-be swimmers: strong currents, deep waters and submerged obstacles.

Yes, but: Philly's Delaware River isn't completely off-limits.

• Certain recreational activities are permitted, like boating and fishing, where bodily contact with the water is unlikely, per the Delaware River Basin Commission.
• However, significant sewage overflows can make the waterway unsafe for any recreation for several days.

☝️ Pro tip: Avoid the Delaware River after heavy rain — whether for kayaking or letting your dog take a dip, PennEnvironment spokesperson Stephanie Wein tells Axios.

• Heavy rain can overwhelm Philly's sewage system, increasing the likelihood of overflows into the river.

Worth noting: The city's Water Department doesn't recommend swimming in any of the city's creeks or waterways.

What they're saying: Wein says pollution levels in the Delaware River around Philly will remain elevated until the sewage overflows are reduced.

• "Philadelphians shouldn't have to go to the Jersey Shore or Poconos to enjoy swimming. They should be able to do it right here in Philly like other big cities," she said.

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Philly is on track to have its fourth-warmest summer on record.

By the numbers: Temps are running roughly 2.4 degrees above average this summer, as of last Thursday.

• Philly has seen 36 days this year when temperatures reached at least 90 degrees — 10 of those in August — Alex Staarmann, meteorologist at the National Weather Service's Mount Holly outpost, tells Axios.

Context: Philly historically averages 30 of those days annually.

Zoom in: Philly has so far logged at least eight heat-related deaths this year, per the city's Department of Public Health.

• Meanwhile, heat streaks in Philly are getting more common each year compared to the 1970s.

Worth noting: Big swaths of the city suffer from the "urban heat island" phenomenon, where buildings, roads and other structures are typically hotter because they trap heat.

The big picture: Philly's hot summer comes as the U.S. just recorded its hottest month on record, per new federal data dating back to 1895.

• July's average temperature was 76.89°F, topping the 76.77°F mark set in July 1936.
• That's 3.3°F warmer than the 1901-2000 average.

What they're saying: "Above-average temperatures covered the entire [contiguous U.S.], with all states ranking in the warmest third of their July temperature records and none ranking near or below average," NOAA's National Centers for Environmental Information said in its monthly report.

Between the lines: A series of "heat domes" trapped warm air over parts of the country in July, fueling extreme heat.

• Researchers have found that climate change is making extreme heat events more common and more intense.

What we're watching: NOAA's Climate Prediction Center is forecasting an elevated chance of above-average temperatures for most of the continental U.S. through August.

• 2026 could also set a new record for the hottest year globally.

🤖 Upper Merion officials put the kibosh on a proposed massive AI data center in the King of Prussia area last week.

• But the developer of the Renaissance Park and Innovation Data Center Campus vows to appeal the decision, so the fate of project is TBD. (6ABC)

An off-duty Philadelphia police officer was fatally shot outside an after-hours lounge in Southwest Philadelphia early Sunday, while a second man was critically wounded.

• The 29-year-old officer had been with the department for two years and was assigned to the 12th District. No arrests have been made. (6ABC)

⚖️ Pennsylvania lawmakers missed a deadline to enact a new sentencing law after the state Supreme Court struck down mandatory life-without-parole sentences for felony murder.

• Nearly 1,100 people are serving those sentences, including more than 500 in Philadelphia, and hundreds could seek resentencing. Philadelphia's public defender estimates handling those cases could cost the city $24 million.

Usually, there's no love lost among UFC fighters.

• But in the City of Brotherly Love, Islam Makhachev and Ian Machado Garry traded respect instead of barbs after going the distance in Saturday's welterweight title bout.

What they're saying: "Ian is a great fighter, a good man, and I respect him," Makhachev said. "He gave me a hard time, but I still prove it every fight."