Following a stretch of dry weather, more humid air and the risk of showers and thunderstorms will spread from the Midwest late this week to the Northeast this weekend.
"The spell of unusually low temperatures and humidity levels for early August will continue in the northeastern United States into Thursday," according to AccuWeather Senior Meteorologist Dave Dombek.
North to northeasterly breezes have allowed cool, dry air to spread over a broad area of of the Midwest and Northeast into Tuesday.
Along much of the Interstate 95 corridor, high temperatures are typically in the middle to upper 80s F with nighttime lows within a few degrees of 70.
Through Thursday in this corridor, highs will generally be in the lower 80s with nighttime lows in the 60s.
In most cases, the weather will still be warm enough for a swim and outdoor activities during the day. Windows can be left open and fans and air conditioners turned off for a while.
As the core of the cool, dry air slides to the east, a southerly flow of more humid air will resume from west to east across the Midwest and Northeast later this week.
However, the rebound in temperatures may lag.
"We do not expect a return of heat any time soon," Dombek said.
"Temperatures may stay below average in some coastal areas, such as New York City, due to cloud cover and a breeze off the ocean."
Some areas well inland in the Northeast and over the Midwest, where the sun is out, may return to near average for a time.
The combination of increasing humidity levels and the approach of a storm system will bring an uptick of showers and thunderstorms.
Portions of the Midwest may experience a shower or thunderstorm as early as Thursday.
Parts of the mid-Atlantic may experience the same Thursday night and Friday. However, any rain is likely to hold off eastern and northern New England until the weekend.
"Even though the pattern will turn unsettled late this week and into this weekend, an all-day washout is unlikely," according to AccuWeather Chief Meteorologist Elliot Abrams.
The storm moving in is not as strong as that which affected parts of the central U.S. last weekend and the mid-Atlantic coast on Monday.
While some of the thunderstorms will have the potential to become heavy and gusty at an isolated level, the storm system is unlikely to produce severe weather over a regional basis.
"Another dose of cool, dry air will sweep into the Midwest this weekend and part of the Northeast early next week," according to AccuWeather Lead Long-Range Meteorologist Paul Pastelok.
However, any reduction in humidity levels and drying in coastal areas of the Northeast may be limited or brief.
"There is the chance a tropical system, currently dubbed 99L, tracks close enough to cause this weekend's showers and thunderstorms to stall along the mid-Atlantic coast into next week," Pastelok said.
Interests along the U.S. Atlantic coast should monitor the progress of 99L, especially this weekend and into next week.