Waltham Weather Outlook: July 9 – July 16, 2026

Warm and humid weather will continue across Waltham through Friday before a cold front brings a chance of showers and thunderstorms Friday afternoon and evening. Temperatures will reach the lower 90s Thursday with dew points near 70°F, producing heat index values in the middle to upper 90s. Friday will remain humid, although temperatures should be slightly lower as clouds increase ahead of the approaching front. Scattered thunderstorms are expected to develop during the afternoon and evening, with frequent lightning and heavy downpours the primary concerns. Slow-moving storms could produce localized street flooding, particularly where repeated thunderstorms move over the same areas. Behind the front, a much more comfortable air mass will settle into southern New England for the weekend, bringing lower humidity, seasonable temperatures, and mainly dry weather. Temperatures begin climbing again early next week, with another period of hot weather likely Tuesday through at least the middle of the week.