Much of the first full week of June will feature cool and unsettled conditions in the northeastern United States, prior to a change in the weather pattern.
People may need to grab umbrellas most days of this week as frequent showers and thunderstorms erupt across the region. Those with outdoor plans, including graduation celebrations and beach and lake visits, may have to duck for cover.
If you hear thunder, seek shelter in a vehicle or fully-enclosed building. Tents and pavilions do not provide proper shelter from dangerous lightning strikes.
"Similar to what has occurred multiple times during May, the jet stream will dip southward over the region this week," according to AccuWeather Chief Meteorologist Elliot Abrams.
The jet stream is a high-speed river of air at the level where jets often cruise at. When it plunges south, like this week, the weather often turns cooler and wetter than average.
"The pattern will cause a storm system to stall nearby," Abrams said.
The storm will cause areas of steady rain. While it will not rain all day every day, cool air aloft will make it easy for clouds to build and showers to erupt on a nearly daily basis.
Where the sun is out for a few hours, the brief warmth can spawn locally heavy, gusty thunderstorms.
Where downpours occur, isolated flash and urban flooding can occur. Where downpours persist, small streams may rise close to bank full.
In parts of the central and northern Appalachians, temperatures will be no higher than the 50s for two to three days.
The core of the coolness will be on Wednesday and Thursday, when high temperatures in the 60s can stretch as far to the south as central Virginia and eastern Maryland.
One area that may escape many days in a row of showery and cool conditions may be part of New England.
"It is possible a wedge of dry air drops in from the northeast across Maine, New Hampshire, Vermont and eastern Massachusetts for a day or two during the middle of the week," Abrams said.
In much of the Northeast, temperatures will begin to stabilize this weekend ahead of much warmer weather next week.
"How long that warmth lasts will depend on whether or not another dip in the jet stream develops," Abrams said.