Waltham Weather Outlook: May 16–23, 2026

After a chilly, gray and damp end to the workweek, a major pattern shift is set to unfold across southern New England over the next several days. A strengthening ridge of high pressure will bring increasingly warm air into the region beginning this weekend, allowing temperatures to climb well above normal by early next week. The overall stretch from Sunday through Wednesday will feature a distinctly early summer feel with plenty of sunshine, warm afternoons, and rising humidity levels. The peak of the heat is expected Tuesday and Wednesday, when temperatures in Waltham could push into the lower 90s. A cold front approaching during the middle of next week may bring the risk for scattered thunderstorms before somewhat cooler and less humid air arrives toward the end of the forecast period.