The New Hampshire Department of Environmental Services issued the first Code Orange air quality alert of 2026 on Tuesday, warning that ground-level ozone in Rockingham County and across higher-elevation parts of the state will reach unhealthy levels through Tuesday evening. The advisory arrived as a heat advisory pushed temperatures across southern New Hampshire toward record territory for May, with Manchester forecast to hit a heat index of 95 degrees by late afternoon according to the National Weather Service forecast office in Gray, Maine.

The alert, originally reported by New Hampshire Public Radio, is the first of the 2026 season but follows a worsening multi-year trend that has caught the attention of state environmental officials, public health professionals, and parents of children with asthma. Last year, New Hampshire experienced nine air quality advisories. In 2023, the count spiked dramatically because of wildfire smoke drifting south from major fires in Canada, and state officials say wildfire-driven advisories have become a regular feature of New Hampshire’s summer air over the past five years.

For the average Granite Stater, a Code Orange designation is more than a bureaucratic label. It is the second-most serious step on the federal Air Quality Index color scale, and it signals air pollution levels considered unhealthy for sensitive groups. Those sensitive groups include children, older Americans, anyone living with lung disease, people with active asthma, and individuals planning prolonged or strenuous outdoor activity. Even healthy adults can experience mild symptoms such as throat irritation, watery eyes, or shortness of breath during a Code Orange day if they spend extended periods exercising outside.

State officials are urging residents in the affected areas to limit outdoor exertion, take more frequent breaks if working outside, and watch for warning signs like shortness of breath, chest pain or palpitations, and difficulty breathing. Coaches running afternoon practices, road race directors, and outdoor camp operators in southeastern New Hampshire have been advised to modify schedules and offer indoor alternatives where possible. The alert is in effect through Tuesday evening and is expected to lift as winds shift and overnight temperatures bring the ground-level ozone formation cycle to a halt.

The science behind Tuesday’s alert is straightforward. Ground-level ozone, the pollutant of concern in this advisory, is not emitted directly. It forms when nitrogen oxides and volatile organic compounds react in sunlight and heat. That chemistry favors hot, sunny, humid days with light winds, exactly the conditions southern New Hampshire is experiencing this week. DES officials note that much of the precursor pollution driving the alert was transported into New Hampshire by southwesterly winds from heavily industrialized corridors in the Mid-Atlantic and Ohio Valley. Local emissions from vehicle traffic on Interstate 93, Interstate 95, and the Everett Turnpike, combined with regional power generation and the unseasonable heat, did the rest.

Rockingham County, home to communities like Portsmouth, Exeter, Salem, and Derry, sits in the path of those transported emissions and is consistently the part of New Hampshire most prone to summer ozone alerts. The state’s higher-elevation locations above 2,000 feet, which include large parts of the White Mountains, are also covered by Tuesday’s alert because ozone tends to mix and concentrate at elevation on hot afternoons. Hikers planning summits on Mount Washington, Mount Lafayette, or the Presidential Range should consider rescheduling strenuous ascents and watch for symptoms while above tree line.

The arrival of the first Code Orange day before Memorial Day is earlier than New Hampshire residents have come to expect, and it underscores a broader shift in the state’s air quality landscape. For decades, New Hampshire benefited from prevailing winds, relatively low industrial emissions, and forested terrain that delivered some of the cleanest air in the Northeast. But warmer springs, expanding wildfire seasons across North America, and the ongoing reality of long-range pollution transport mean Granite Staters are now confronting more frequent advisories than they did a generation ago. Officials at DES have repeatedly emphasized that wildfire smoke from Canadian fires has started to affect New Hampshire significantly more in the last five years than at any point in modern memory.

What can residents do beyond watching the alerts? Public health agencies recommend keeping windows closed during peak ozone hours, generally late morning through early evening, running central air conditioning if available, and avoiding strenuous outdoor exercise during alert periods. People with asthma should keep rescue inhalers nearby and follow their established asthma action plans. Parents of young children, particularly those with respiratory conditions, should consider moving outdoor playtime to early morning when ozone levels are lowest. For Granite Staters considering investments in indoor air quality, HEPA-rated air purifiers with activated carbon filters can help reduce indoor pollutant levels during smoke events, though ozone itself is harder to filter and is best avoided by limiting outdoor exposure.

The alert also fits into a larger conversation playing out across New Hampshire about climate resilience, public health preparedness, and the practical steps families can take when conditions outside change quickly. Residents preparing for summer should plan for the reality that ozone alerts and wildfire-smoke episodes are likely to recur. Building a home preparedness kit is a year-round project, and the spring is a good moment to refresh medications, check air filters, and review household plans. New Hampshire has also been navigating significant environmental policy debates this session, including federal forest-management changes that intersect with wildfire risk and regional air quality.

Tuesday’s heat is forecast to ease by Wednesday morning as a cold front moves through northern New England, bringing scattered thunderstorms and cooler air to the Seacoast. That cooler, breezier pattern should clear out the ozone and lift the Code Orange designation. But forecasters and state officials caution that this is likely the first of many summer alerts. With a hot, dry summer outlook for the Northeast and active wildfire conditions already developing in eastern Canada, Granite Staters should be prepared to see additional advisories rolling out in June, July, and August.

For real-time air quality readings and forecast information, residents can check the DES airdata portal or use the federal AirNow website and mobile app, which provides hour-by-hour readings for monitoring stations across the state. Local broadcast forecasts from National Weather Service offices in Gray, Maine and Taunton, Massachusetts also include air quality information during alert periods, and DES typically issues advisories the afternoon or evening before an alert day takes effect.

The bottom line for New Hampshire residents: take Tuesday’s alert seriously, especially if you or someone in your household falls into a sensitive group, but also recognize that this kind of day is going to be part of the new normal. Knowing the warning signs, having a plan for hot afternoons, and paying attention to official forecasts are no longer optional.