Records in jeopardy as Bermuda high sends temperatures soaring in the Lehigh Valley

BETHLEHEM, Pa. — Temperature records will be in jeopardy Thursday across the region, with highs expected to push into the upper 80s in the Lehigh Valley.

Forecast highs currently match or exceed the daily record at multiple climate sites, the National Weather Service said in its morning forecast discussion.

The record high to beat in Allentown is 88 degrees, set in 1941.

• Temperature records are in jeopardy Thursday across the region
• It's all thanks to a Bermuda high, a pattern that pumps heat and humidity into the area
• Fire weather continues to be a concern due to a combination of low relative humidity, westerly winds and dry fine fuels

"Sunshine will be plentiful through the day today, with an otherwise pleasant day accompanied by very low humidity once again, and fire weather will be the main concern,” the weather service forecast discussion said.

A similar day is expected Friday, meteorologists said, though cloud cover could put a cap on the warmth.

What’s driving the summerlike warmth?

Highs and lows in the Lehigh Valley are running about 20 degrees above the historical average for the middle of April.

It’s all thanks to a broad high-pressure system centered off the coast of the Southeast United States extending back toward the southern and central Appalachians, forecasters say.

It’s called a Bermuda high, and it pumps tropical air into the region. Typically, this kind of pattern is more dominant during the summer — when it brings both heat and humidity.

Why?

The high-pressure systems are near Bermuda and can strengthen and shift directions. They also have a clockwise circulation, which means the eastern United States gets south to southeast winds, bringing the heat and humid air from the Atlantic Ocean and Gulf of Mexico into our region.

In the summer, that type of pattern often leads to heat waves. But since it’s the middle of April, the heat will quickly be cut down.

A widespread chance of showers is expected Saturday, and the weather service said the longer-term period looks a bit unsettled through the early portion of next week.

Fire weather continues

There continues to be an elevated risk of wildfire spread across the region, thanks to a combination of low relative humidity, westerly winds and dry fine fuels — small twigs, leaves, needles, grasses, ferns or similar material.

All of those can ignite and burn quickly when dry, and they are conducive to fairly quick fire spread, the weather service warned.

Residents are urged to use caution if handling potential ignition source outdoors, including machinery, cigarettes and matches.