FRIDAY: There will be partly cloudy skies and temperatures will get to between 87-92 degrees. If Boston hits 90, its the second official heatwave of the season. Storms will develop in western New England later in the day and be in western Vermont by 4-8PM. Don't worry about these storms here in eastern New England. Boston's showers and storms will likely hold off until Saturday.
SATURDAY: Showers and thundershowers will be possible, for all of New England with the best chance of showers and thundershowers after 1PM. Some of the storms could have heavy rainfall. Highs will be in the 83-88 range, coolest down on the Cape.
SUNDAY: The wettest day of the next several with heavy rainfall. Highs should get to around 80 in Boston, but temperatures in the 70's will be found along the North Shore and Cape. Rockport, MA may stay in the upper 60's.
Thereafter, the rain showers will likely stay for Monday and Tuesday, too early to say just how widespread or heavy these showers will be. Temperatures throughout the period will likely be in the 80's, just regular summer weather.