Boston started Tuesday, June 30, on a deceptively pleasant note, with mild temperatures and mostly sunny skies. That breather will not last long. Highs are expected to reach near 89 today, and a much hotter, potentially dangerous stretch is lined up for midweek. Forecasters say the worst of it should hit right in the Fourth of July window, with peak heat Thursday and Friday.
Hot This Afternoon
This afternoon stays mostly sunny, with a high near 89 and a south breeze around 5 to 14 mph. Humidity will creep up through the day, turning the city into more of a slow simmer by evening. Late tonight, mainly after 9 p.m., there is a chance of showers and a few thunderstorms, with the overnight low only dropping to around 72.
The National Weather Service has already pulled the alarm, issuing an Extreme Heat Warning from 10 a.m. Wednesday, July 1, through 8 p.m. Saturday, July 4. You can dig into the full, technical breakdown from NWS Boston.
Dangerous Heat Wednesday Through Saturday
From Wednesday through Saturday, the heat moves from uncomfortable to genuinely hazardous. Away from the immediate coast, temperatures are forecast to surge into the upper 90s, with readings around 98°F on Wednesday and highs near 99°F on both Thursday and Friday. Heat index values are expected to push well into the triple digits, making it feel even more oppressive.
Nights will not offer much relief. Lows are projected to hang in the mid to upper 70s, and parts of the urban core may only slip to around 80. That kind of persistent warmth ramps up the risk of heat-related illness, especially for older adults, infants, outdoor workers and anyone living without reliable air conditioning.
Because this is shaping up to be a prolonged and humid stretch, health officials advise treating the midafternoon like a no-go zone for strenuous outdoor activity. If you need to be outside, take breaks, find shade when you can and watch closely for signs of heat exhaustion, such as dizziness, nausea or heavy sweating that suddenly stops.
Cooling Resources And Safety
For residents without dependable air conditioning, the City of Boston points to BCYF community centers, libraries and some pools as key cooling options during extreme heat events. The city also encourages people to sign up for AlertBoston for heat-related updates and to check in on neighbors and anyone who might be especially vulnerable.
Staying safe in this kind of heat means going back to basics: drink water regularly, even if you are not feeling thirsty; skip alcohol and heavy meals during the hottest parts of the day; and never leave children or pets in parked cars, even for what seems like a quick errand. Details on official cooling centers and more heat-health tips are available through Boston’s heat resources at the City of Boston.
Independence Day Outlook
Looking ahead to Saturday, July 4, the holiday itself is expected to be mostly sunny and hot, with a high near 93. There is a chance of showers or thunderstorms after 2 p.m., so it is wise to plan fireworks, barbecues and other gatherings with shade, plenty of water and some kind of backup plan in case storms roll through.
Boaters should keep a close eye on updated conditions as the day goes on, and anyone with medical vulnerabilities may want to spend the afternoon peak in air-conditioned spaces. If you are determined to celebrate outdoors, pace yourself, stay hydrated and treat the heat as seriously as the holiday.
