A KGUN 9 report this week confirmed what anyone stepping outside in Tucson already knew: an Extreme Heat Warning is in effect as temperatures push toward 110°F. The National Weather Service issues those warnings — not advisories, warnings — when high temperatures are expected to cause serious illness or death in healthy adults with ordinary activity levels.

That threshold matters. An Excessive Heat Watch says conditions are possible. An Excessive Heat Warning says they are happening. At 110°F with typical Southern Arizona humidity, a human body stops cooling efficiently within minutes of direct sun exposure. This isn't a comfort issue. It's a physiology issue.

What 110°F actually stresses in your household

The obvious risk is personal heat illness. The less-discussed risk is infrastructure cascade.

When grid demand peaks across Tucson and the broader APS and TEP service areas, voltage fluctuations happen before outages do. Those fluctuations are hard on HVAC compressors already running near their design limits. A compressor that fails at 3 p.m. on a 110-degree day in August means a house interior that reaches 95°F within two to three hours in typical Arizona construction — faster in older or poorly insulated homes.

Refrigerated food follows a predictable timeline after power loss: the FDA's four-hour rule holds at normal temps, but ambient heat accelerates bacterial growth well beyond that. A freezer full of meat becomes a decision point, not a guarantee, within hours.

Water lines and storage also respond to extreme heat. Outdoor hose bibs and above-grade plumbing can deliver hot — sometimes scalding — water for the first minute of flow during heat events. Rooftop solar water heaters common in Tucson can superheat storage tanks during sustained high-temperature periods.

What we'd actually do

Get eyes on your HVAC system before the next warning, not during it. Change your air filter if you haven't in the last 30 days. A clogged filter forces the blower motor to work harder, reduces airflow across the evaporator coil, and can cause the unit to freeze up and shut down. This is a five-minute task that can prevent a four-day repair wait during peak season.

Identify your nearest public cooling center now, not when you need it. Pima County operates a network of cooling centers — libraries, community centers, and dedicated sites — during heat emergencies. The county's heat-relief page lists current locations and hours. Write down two addresses. If your power goes out, your phone battery will eventually follow, and you won't want to search for this information at hour three without AC.

Pre-position water and ice for a 24-hour outage scenario. Fill every reusable bottle and container you own the night before a warning is forecast. Put two or three two-liter bottles of water in your freezer. If power drops, those frozen bottles extend your food window and can serve as personal cooling tools. This costs nothing beyond the time it takes.

Check on your most heat-vulnerable household members before noon. Heat illness moves fast in people over 65, children under five, and anyone on diuretics, antihistamines, or antipsychotics — all drug classes that blunt the body's cooling response. A morning text or call to elderly neighbors or relatives takes 60 seconds and can catch warning signs before they escalate.

Know your car's limits as a cooling refuge — and its risks. Many Arizona households use their vehicle as a backup cool space during brief outages. That works, but a car interior can exceed 130°F within 20 minutes when parked. If you're using your vehicle for cooling, keep it running with AC on, stay in shade when possible, and never leave children or pets inside an idling car unattended.

The bigger frame

Tucson's heat isn't new. What's changing is the duration and density of extreme-heat days within each summer season — a pattern documented in recent Arizona Department of Environmental Quality climate monitoring data. For households, that shift means the gap between "uncomfortable summer" and "household emergency" is narrowing. The families who navigate this well aren't the ones with the most gear. They're the ones who made a few decisions during a calm week: they know where the cooling centers are, they keep the HVAC filter current, and they've thought through what happens at hour one, hour four, and hour eight of a power loss.

Durability in a desert is mostly unglamorous. It's a clean filter, a written address, and a phone call before noon.