For most heatwaves: plan for 3 to 7 days. That’s the typical lifespan of a heat dome before it wobbles away.
But if you’re in a city like Phoenix or Austin? Add a few more days. Urban areas create “heat islands” (read: concrete ovens).
Dangerous Heat Wave to Last 7-10 Days, Heat Indexes Reaching 107° In
Here’s a cheesy but true rule: the hotter it is at night, the longer the heatwave. If your 11 PM walk feels like a sauna, buckle up.
Why You Should Care About Night Temps
Daytime highs get all the glory. But nighttime lows are the real story. If temps don’t drop below 80°F (27°C), your body never recovers.
That’s when you start sleepwalking to the fridge. It’s also when power grids start sweating. Everyone cranks the AC at once, and the system cries.
Advice? Set your thermostat to 78°F. It’s not sexy, but it might keep the lights on.
