By Lauren Casey

PHILADELPHIA (CBS) — Dangerous heat has returned to the Delaware Valley and will persist into midweek. A heat advisory is in effect for Philadelphia and surrounding counties, Berks County, and the Lehigh Valley until 8 p.m. on Tuesday.

The high temperature in Philadelphia surpassed 90 degrees today for the second consecutive day and for the fifth time this month. These stats pale in comparison to the number of dog days last month. The 18 90-degree days last month is now tied for the fourth-most on record for July.

So far this year, we’ve tallied 28 days with 90-degree heat, one day shy of the yearly average. These days of excessive heat are though waning. The average date of our last 90-degree reading is Sept. 1.

The latest date on record is Oct. 10, in 1939.