Second Heat Dome Bakes the West: Palm Springs Nears 117°F, Phoenix Stuck Above 110°F

The West's turn has come. A second heat dome settled over the western and central United States beginning July 6, one day after the first dome finished baking the East, and it has pinned the desert Southwest under some of the most dangerous temperatures of the year. Palm Springs and the Coachella Valley faced forecast highs of up to 117°F Thursday into Friday, while Phoenix ran at 113°F for three straight days and, forecasters warned, may not see a daily high below 110°F for a week.

As of July 12, 2026, the numbers behind that forecast are stark, and so is the human cost already on the books. The Phoenix Fire Department has responded to roughly 400 heat-related calls since May 1, and 18 people in the Phoenix area have died of heat-related causes so far this year — more than three times the 5 recorded by this point in 2025. For residents across Arizona, Nevada, and the California deserts, this is the stretch of summer when routine decisions about hydration, cooling, and time outdoors become genuinely consequential.

A Second Dome in as Many Weeks

Heat domes are ridges of high pressure that trap hot air in place, compress it, and cook it further. The first of this summer's back-to-back domes sat over the eastern United States through July 5. The second built over the western and central part of the country starting July 6, and it has proven both broad and stubborn.

The footprint is large. Arizona, Nevada, New Mexico, Texas, Arkansas, California, and Florida have all seen temperatures near or at triple digits under this pattern. But the sharpest edge of the heat is in the low deserts, where the dome's compression stacks on top of terrain that is already the hottest in the country in mid-July.

What distinguishes this event from an ordinary desert summer is persistence. A 113°F afternoon is survivable; a week of them, with no meaningful overnight relief, is a different kind of hazard. That is the setup the Southwest is in now.

The Numbers Across the Desert Southwest

Phoenix hit 113°F on July 6, 7, and 8, and the city did not drop below 90°F at night during that stretch. The forecast called for midday readings climbing as high as 115°F, with daily highs potentially holding at or above 110°F for a week straight.

To the south, Tucson has been under an extreme heat warning with temperatures running 107°F to 111°F. Tucson typically runs a few degrees cooler than Phoenix, but at these levels the distinction matters little for the human body.

West of the Colorado River, the picture is hotter still. The Palm Springs and Coachella Valley forecast topped out around 117°F for Thursday and Friday, and the desert communities east of San Diego faced similar readings. At the bottom of the Grand Canyon, Phantom Ranch — a destination that draws hikers down a mile of elevation into an oven — was forecast to reach 111°F to 114°F through Saturday.

Southern Nevada sits squarely inside the dome as well. Las Vegas and neighboring Henderson share the same dry-heat profile as Phoenix and face the same core risks: extreme afternoon temperatures, warm nights, and a long duration of exposure with no built-in break.

Why Nights in the 80s Are the Quiet Killer

The most important number in this event may not be 117. It is the overnight low. Across the region, nighttime temperatures have been holding in the 80s — and in Phoenix, above 90°F on the hottest nights. That eliminates the body's most important recovery window.

Human heat tolerance is cumulative. During a hot day, core temperature rises and the cardiovascular system works hard to shed heat through sweating and increased blood flow to the skin. Cool nights let the body reset. When the low never falls out of the 80s, that reset never fully happens. Each day of the heat wave begins with a body that is already partially depleted, and the stress compounds.

This is why heat waves kill more people in their later days than their first, and why the elderly, people with heart and kidney conditions, outdoor workers, and anyone without reliable air conditioning are at escalating risk as a dome persists. A person who managed fine on day two may be in trouble by day six, even if the thermometer reads the same.

Warm nights also strain homes. Buildings that would normally shed heat after sunset stay warm, air conditioners run continuously, and residents without cooling — or with units that cannot keep up — have no natural relief to fall back on.

The Human Toll Is Already Running Ahead of Last Year

The clearest signal of how dangerous this summer has become is in the emergency data. Phoenix firefighters have handled roughly 400 heat-related calls since May 1, and the department reports that crews are now using cold-water immersion — submerging severely overheated patients to bring core temperature down fast — every day, across the entire city. Cold-water immersion is a last-resort field treatment for heat stroke, and its daily use citywide is a measure of how many people are reaching a medical crisis.

The death toll tells the same story. Eighteen people in the Phoenix area have died of heat-related causes so far this year. By this point last year, that number was 5. That is not a rounding difference; it is a more-than-threefold increase, and the hottest weeks of the summer are only now arriving.

Officials have responded by cutting off some of the most dangerous exposure at the source. Extreme heat has closed hiking trails in the Phoenix area, a step aimed at the steady stream of rescues that mountain parks generate when visitors underestimate desert conditions. The Phantom Ranch forecast of 111°F to 114°F is a reminder that some of the region's most iconic outdoor destinations are, right now, among its most hazardous.

What Dry Heat Means — and Why Evaporative Cooling Still Works

There is one piece of genuinely useful news for the interior West: this is dry heat, and dry heat can be fought with evaporation. In humid conditions, sweat cannot evaporate efficiently and the body's primary cooling mechanism fails. In desert air, evaporation works — which means several low-cost strategies remain effective here that would be useless in Houston or Miami.

Evaporative coolers, the "swamp coolers" common in Southwestern homes, function well in low humidity and use a fraction of the electricity of refrigerated air conditioning. For households worried about utility bills during a week of continuous cooling, or in older homes without central air, a working evaporative cooler is a legitimate defense in this air mass. The same physics applies to the body: a damp shirt, a spray bottle and a fan, a cool shower, or wet cloths on the neck and wrists all pull heat off the skin quickly when humidity is low.

The catch is that evaporation only helps a body that has water to spare. Dry heat dehydrates people faster than they perceive, because sweat evaporates instantly rather than accumulating. Thirst lags behind need. In conditions like these, hydration has to be scheduled rather than felt — steady water intake through the day, more during any outdoor activity, and attention to electrolytes for anyone sweating for extended periods.

Dry heat also deceives. The absence of oppressive humidity makes 110°F feel more tolerable than it is, which is part of why trail rescues and heat-stroke calls spike in the desert Southwest even among healthy, experienced people.

Cooling Centers: The Backstop for Those Without AC

For residents whose homes cannot stay safe — no air conditioning, a broken unit, or bills that make continuous cooling unaffordable — the public backstop is the cooling center network. Cities across the region open libraries, community centers, and dedicated relief sites during heat emergencies, offering air conditioning, water, and a place to spend the hottest hours.

Our national cooling center finder lists locations by state and city. Residents in the hardest-hit metros can go directly to the Phoenix cooling center list, or the Tucson and Las Vegas listings to find the nearest open site.

The people most likely to need a cooling center are often the least likely to seek one out: older adults living alone, people wary of leaving pets, and those who have "gotten through" past summers without help. A week of 110°F-plus days with no overnight recovery is not a summer to tough out. Checking on isolated neighbors and relatives — and offering a ride to a cooled space — is one of the most effective interventions available to ordinary residents.

What Happens Next: Records, the Grid, and Dry Lightning

The pattern is not finished. Forecasts issued July 11 pointed to another western build of heat, with all-time records at risk and temperatures up to about 43°C — roughly 109°F and higher — spread across the western and north-central United States. That would push extreme heat beyond the desert floor and into regions where homes, infrastructure, and residents are less adapted to it.

Two secondary hazards ride along with that forecast. The first is power-grid strain: a continent-scale hot spell drives simultaneous peak demand across many states, and an outage during a heat emergency converts an uncomfortable event into a life-threatening one within hours, especially for anyone dependent on electric cooling or medical equipment. The second is wildfire risk from dry thunderstorms — storms that produce lightning but little rain, striking landscapes that the heat has already cured into fuel.

For water systems, sustained extreme heat lands on the demand side of the ledger. Outdoor watering, cooling loads, and evaporation all climb together during a dome like this, which is why heat events and watering rules so often tighten in tandem across the Southwest. Residents in Henderson, Las Vegas, Phoenix, and Tucson should assume their existing watering schedules remain fully in force during the heat and check their city's page for current rules before adjusting irrigation.

What Residents Should Do Now

• Shift outdoor work and exercise to dawn. With highs of 110°F to 117°F and warm nights, the only relatively safe outdoor window is early morning. Treat closed trails as closed — the closures exist because rescues at these temperatures endanger crews as well as hikers.
• Hydrate on a schedule, not by thirst. Dry air evaporates sweat before you notice it. Drink water steadily all day and add electrolytes during prolonged sweating.
• Use evaporation to your advantage. In this dry air mass, swamp coolers, fans paired with damp skin or clothing, and cool showers all work well and cost little to run.
• Protect the overnight hours. If your home will not cool below the mid-80s at night, sleep in the coolest room, use fans and damp sheets, and consider a cooling center or an air-conditioned friend's home for the worst nights.
• Know the warning signs. Confusion, dizziness, nausea, a racing heart, or skin that stops sweating signal a medical emergency. Call 911 and cool the person aggressively with water while help is coming — the same principle behind the immersion treatment Phoenix crews are now using daily.
• Check on vulnerable people every day. Older adults, outdoor workers, pregnant women, young children, and anyone without air conditioning need daily contact during a stretch like this.
• Prepare for a possible outage. Keep water stored, devices charged, and a plan for where you would go if power fails during peak heat.

The Week Ahead

The next several days will show whether this dome breaks down or hands off to the even broader heat episode that forecasters flagged on July 11, with all-time records in play across a wider swath of the West. Either way, the season's trajectory is already set by the numbers Phoenix has posted: emergency calls in the hundreds, a death toll far ahead of last year's pace, and weeks of peak summer still to come. We will continue tracking daily conditions, cooling center availability, and any changes to local watering rules across the affected states as the pattern evolves.