Significant Weather Weekly Outlook
Excessive Heat Likely for Mid to Late Week
NWS has Issued an Excessive Heat Watch for Nearly All of Southern New England
The big weather story is the hot weather ahead. Hot and humid conditions are expected mid to late week with high confidence. A robust upper ridge of high pressure will build into our region and effectively lead to a large heat dome over most of the United States east of the Mississippi River. Temperatures over much of southern New England (outside of the Cape and Islands and perhaps very immediate south coast) may approach the upper 90s to around 100 degrees Wednesday, Thursday, and Friday with dewpoints in at least the mid to upper 60s. Heat indices may exceed 105 degrees mid to late week for much of southern New England during the day, and overnight temperatures will remain uncomfortably warm (likely not dropping below the 70s). This heat may prove dangerous for many including the elderly, very young, people exerting themselves outdoors, and the medically compromised. Undertake precautions and check on those who may be more vulnerable.
The heat and humidity will likely cause a more unstable atmosphere with a risk of afternoon/early evening thunderstorms, although confidence is presently rather low on coverage and timing. Broad subsidence associated with the upper ridge may inhibit afternoon thunderstorms for a period – perhaps most likely Wednesday and Thursday afternoons. Adding even more to the complexity of any thunderstorm forecast is a possibility of a mesoscale convective system (MCS) developing in south central Canada and moving along the periphery of the building upper-level high pressure ridge somewhere in the Northeast Tuesday night in conjunction with a shortwave upper trough. Still another MCS may form and move southeast through some portion of New England Wednesday night (likely further to the northeast as the ridge builds). Confidence is low on any MCS actual formation and track across the Northeast. At least a portion of southern New England may be impacted one or both nights. A MCS is typically characterized by a large cluster of thunderstorms with gusty winds, frequent lightning, and torrential downpours. By Friday afternoon, the upper ridge is expected to begin to erode with possibly another shortwave trough aloft moving along the periphery of the decaying boundary of the upper-level high pressure area. This could provide the triggering mechanism for more organized (and possibly strong to severe) thunderstorms Friday and/or Saturday.
Early indications point toward a slight cooling trend next weekend followed by greater cooling the first part of the following week as the upper ridge over our area continues to weaken.
In summary, expect dangerous heat Wednesday through Friday. Also, one can expect at least one or two episodes of thunderstorms this week, but confidence at this point remains low on timing, coverage, and intensity.
Next Message
A weather blog or blogs may be issued this coming week due to the high potential of excessive heat or if there looks to be a significant risk for severe thunderstorms. The next significant weather weekly outlook is scheduled for Monday July 6. Be safe. Wish all of you a Happy 4th of July and 250th birthday of our nation.
About this Blog and Disclaimer
The National Weather Service monitors the weather 24/7 and updates forecasts, watches, and warnings as necessary. For most of southern New England, refer to your local Weather Forecast Office for the latest forecast/warning information at weather.gov/box. For information from other Weather Forecast Offices, go to weather.gov and click on the location of interest on the map.
The frequency of this blog will depend upon the nature of the weather threat and availability of the author. Thus, for the latest information on weather forecasts and warnings, refer to the National Weather Service, which monitors and forecasts the weather 24/7.
Blue Hill Observatory and Science Center (BHOSC)
The BHOSC maintains a continuous daily observation record that dates from February 1, 1885 without interruption and provides educational information on weather and climate to area students and the community at large. Your support of BHOSC is much appreciated and enables this nonprofit organization to maintain the long-term climate record at the Blue Hill Observatory (longest continuous record in North America) and provide valuable educational resources on weather and climate via outreach to schools, site visits/tours, webinars, and conferences. For more information on the Blue Hill Observatory and Science Center, explore bluehill.org.
Message issued June 29, 2026 by:
Bob Thompson
Retired National Weather Service Meteorologist
Blue Hill Observatory and Science Center Board member
