Waltham Weather Outlook: June 12 – June 20, 2026

Summer arrives in earnest across southern New England over the next several days as the warmest air mass of the season overspreads the region. Temperatures will climb into the upper 80s and lower 90s through the weekend, accompanied by increasing humidity. While much of the period will feature dry weather and ample sunshine, a few opportunities for showers and thunderstorms exist, particularly Friday night and again late Sunday into early Monday. Following the weekend heat, temperatures moderate somewhat early next week while remaining above seasonal averages. Forecast confidence decreases later in the period, but the overall pattern favors continued warmth with lower humidity compared to the weekend.