Forecasters are warning Philadelphians to be prepared for a hot end to an already-steamy work week.

The National Weather Service has issued an "excessive heat warning," in place from noon Thursday until 8 p.m. Friday.

High temperatures in the mid-to-high 90s are expected on both days, with heat index values — the "real feel" temperature — between 98 and 105 degrees.

The remainder of the work week is also expected to be muggy, and overnight lows are forecast to only drop into the mid-to-high 70s.

But the high temperatures are not slated to set any records: The record high for July 20 stands at 99 degrees, set in 1930, and the daily record for July 21 is 103 degrees, also set that year, according to weather service records.

The city's fifth heat wave of the summer will become official Thursday, following highs of 91 degrees Tuesday and 96 on Wednesday. The weather service's alert for Thursday and Friday marks the second time the agency has issued an excessive heat warning this season.

Officials say people should take care if they work or spend time outside, wear light or loose-fitting clothing, drink plenty of water, take frequent rest or cooling breaks and check on elderly neighbors and relatives.

The Philadelphia Corporation for Aging is operating its heatline (215-765-9040) to answer questions and aid callers with heat-related problems from 3 p.m. to 11 p.m. Thursday and 8:30 a.m. to 11 p.m. Friday.

Amid the heat, authorities routinely caution Philadelphians to avoid using fire hydrants to cool off. For decades, the Water Department has been stressing the message: "Hydrants are for fires, not for fun." Here's a public service announcement from the 1980s.

For those seeking an authorized water source, here is a list of pools in the city, which will offer open swim 11 a.m. to 7 p.m. due to the heat wave.

An air-quality alert is also in place for the region, with air pollution levels considered unhealthy for sensitive groups, such as children, people with asthma or heart or lung disease, and the elderly.