The National Weather Service has issued a tornado watch until 8 o'clock tonight for Delaware, South Jersey and Southeastern Pennsylvania.

The watch, which was issued about 3 p.m., means that conditions are favorable for severe thunderstorms that could produce tornadoes.

Looking ahead, a heat wave of sorts is predicted to start Friday, with highs reaching the 90s over the weekend.

Tomorrow, there's a chance of showers with a high in the low 80s.

Then the highs will challenge or exceed 90 degrees for four straight days, with Saturday anticipated as the hottest day of the year so far, reaching into the mid-90s.

With high relative humidity expected, heat warnings and advisories could be issued.

Contact staff writer Peter Mucha at 215-854-4342 or pmucha@phillynews.com.