It is very cold outside. In case you need any additional evidence of that (other than, you know, the fact that Philly looks like it's currently inside a snow globe), check out the Schuylkill River. In case you haven't noticed, it's frozen.

Is the Schuylkill River polluted?

For several decades, the highly acidic waters draining naturally out of the abandoned coal mine flowed into the Schuylkill River coloring it bright orange and bringing iron deposits, heavy metals and other solids which pollute the river and interfere with public uses.

Can you swim in the Schuylkill River?

Swimming and bathing in rivers, streams, and waterways in Philadelphia is not permitted under city ordinance. Both the Delaware River and the Schuylkill are tidal rivers, with strong undercurrents, and, at least around the city's perimers, their water is too dirty for swimming or fishing.