Highest Heat of the Season to Date Expected the Next Few Days
Isolated Strong to Severe Thunderstorm Threat Northern/Western MA Tuesday Afternoon
Broader Risk for Scattered Strong to Severe Thunderstorms Wednesday Afternoon/Early Evening
Heat
Today will feature hot temperatures near 90 degrees over interior southern New England and cooler temperatures in the 70s across coastal areas due to onshore flow. Tuesday and Wednesday will feature hot temperatures in the 90s except cooler along the south coast including the Cape and Islands where the southwest flow will be moderated by cooler ocean water. This will be our first bout of hot weather this season. Under considerable sunshine, a few high temperature records may be broken Tuesday. Some increase in humidity may be noticeable Tuesday night and Wednesday. Cooler temperatures close to seasonal normals are expected Thursday into the weekend.
Thunderstorms
The very warm temperatures will cause the atmosphere to become unstable Tuesday and Wednesday afternoons. Although there is no widespread lifting mechanism expected Tuesday afternoon, the instability alone possibly combined with some weak upper-level energy may be enough to set off isolated strong to severe thunderstorms Tuesday afternoon across portions of northern and western MA. These storms are likely to be localized and of the pulse variety (short-lived). Stronger and more widespread thunderstorms may develop Tuesday afternoon/evening across upstate New York and Vermont, closer to an approaching cold front.
A risk for scattered strong to severe thunderstorms exists for essentially all southern New England Wednesday afternoon into early evening. On Wednesday in addition to the thermal instability (very warm near the surface and colder aloft), there is likely to be more wind shear that could result in more organized storms. Also, an approaching cold front will provide some general uplift to aid in thunderstorm development. Where the strongest thunderstorms develop will likely be determined by the timing of the cold front moving toward our region. Some of the latest model guidance suggests that the cold front (and a prefrontal surface trough) may be approaching southern New England early enough for the strongest storms to affect southern and eastern sections of southern New England, but it’s too soon to be very sure of that.
The main threat from any severe thunderstorms is likely to be highly localized damaging wind gusts. Large hail would be a secondary threat. Keep in mind, however, that any thunderstorm poses a risk for dangerous lightning. Seek safe shelter when thunder is heard. To discern how far away the lightning is, remember that every 5 seconds between the lightning flash and sound of thunder correlates to a mile (e.g. ten seconds between lightning and thunder indicate a lightning strike about 2 miles away). Thunderstorms Tuesday afternoon and Wednesday afternoon/evening may also contain very heavy downpours.
Memorial Day Weekend
The holiday weekend will likely feature seasonable temperatures. Although no severe weather is expected, there could be a risk of one or two bouts of showers. It’s too soon to have much confidence in the duration and areal extent of any shower activity.
Next Message
Will probably issue another message Wednesday morning to more clearly delineate the severe thunderstorm threat for later that day. It’s not the intent of this blog to track individual severe thunderstorms. For latest information when thunderstorms are developing, consult the latest radar imagery from the National Weather Service (or via your favorite app) and monitor any warnings or statements from your local National Weather Service (for most of southern New England, go to: weather.gov/box).
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 May 18, 2026 by:
Bob Thompson
Retired National Weather Service Meteorologist
Blue Hill Observatory and Science Center Board member
