Unhealthy Heat Forecast
Use this tool to see the 7-day heat forecast for Massachusetts. You can also select your city or town using the dropdown menu. The chart shows today’s temperature, the hottest day coming up, and a color-coded forecast for each day. Green means the temperature will be below 78F. Yellow means the temperature will be between 78F and 84°F. Orange means it will go 85°F or above. This can be unhealthy, especially for those sensitive to heat. Red means the temperature will be 85F or above for 3 or more days. When there are red days forecast, the Department of Public Health issues an unhealthy heat alert. This alert is for healthcare workers, local governments, and community groups. They use it to plan, prepare, and act.
Heat Thresholds
| Color | Forecast | Impact |
|---|---|---|
| Green (Below 78°F) | No significant heat-related health risks |
| Yellow (78°F - 84°F | Low threat; heightened awareness encouraged. |
| Orange (85°F or above for 1-2 days) | Medium threat level, urging communities to begin implementing heat mitigation measures. |
| Red (85°F or above for 3 or more consecutive days) | High threat, triggering a Community Heat Alert and activation of response efforts. |
Climate Change, Extreme Heat, and Unhealthy Heat Forecasts
Climate Change and Extreme Heat
Climate change is driving more frequent, intense, and lasting extreme heat events in Massachusetts and across the country. Since the early 1900s, Massachusetts has warmed by nearly 3.5°F, and models experts project a continued rise. By 2050, the number of days above 90°F in the state is expected to double or even triple compared to historical averages. These rising temperatures are not only uncomfortable; they also pose serious health and infrastructure challenges, especially in urban and underserved areas.
In Massachusetts we are not as used to or prepared for extreme heat the way southern and western states are. While we are more used to cold weather and preparing for snow, extreme heat is a newer public health concern for Massachusetts residents.
The First is the Worst
In Massachusetts, extreme heat is becoming a more serious health concern as summer temperatures rise year after year. Data show that the first heat wave of the season is often the worst for people’s health, leading to more heat-related illnesses and hospital visits than later heat waves. This is because our bodies need time to adjust to the heat. That’s why it’s important to prepare early—before the first hot days arrive.
When it is hot, it is usually humid
In Massachusetts, heat often comes with high humidity, which makes hot weather feel even hotter. This "feels like" temperature is known as the heat index. It usually tracks the actual temperature closely, rising and falling together about 97% of the time. Because temperature data is easier to access and understand, it’s a reliable way to track heat risk.
Unhealthy Heat Threshold
When we compared heat waves over several prior summers, our data show that when temperature rises to 85°F or more for three days in a row, there is a significant increase in emergency room visits and heat-related illnesses. The Unhealthy Heat Threshold (85°F for 3 or more days) identifies predictably significant health impacts and was consistent across summers.
Unhealthy Heat Alerts and Forecast Page
Temperatures of 85°F for 3 or more days in a row will trigger an unhealthy heat alert notifications for healthcare professionals, local governments and other community and state organizations so they can plan, prepare, and act. Our Unhealthy Heat Forecast page has a status banner that tracks daily and weekly levels of heat in each city and town in the state. The banner turns red when an Unhealthy Heat Alert is active and shows when high temperatures may pose a greater risk for vulnerable people like children, older adults, and those with chronic medical conditions.