Scorpion season in Arizona runs roughly March through November. Scorpions emerge from winter shelter in March and April as ground temperatures climb, activity peaks from June through September when monsoon humidity arrives, and sightings taper off through November as nights cool.
The driver is simple biology: scorpions are ectotherms, so their activity tracks the temperature of the ground they live on. The rule of thumb is that surface activity picks up once ground temperatures hold above about 70°F — in the East Valley, the first stretch of warm spring nights flips the switch.
Knowing the calendar matters because the best window for some of the most effective scorpion work is not the peak — it is the off-season, when bark scorpions are clustered and stationary. Here is the full year.
The 70-degree trigger
This is why the season's start date moves a little every year. An early warm spell in late February can produce March sightings; a cool spring pushes the wave into April. Watch overnight lows, not the calendar.
Month by month
The monsoon, from mid-June through September, is the height of the season. Humid nights bring out the crickets, roaches, and moths scorpions feed on, and the moisture lets scorpions stay surface-active longer without drying out. More humidity means more prey and more hunting hours, stacked on the year's warmest ground.
October: activity tapers as overnight lows slide. November: most surface activity ends, though warm spells produce stragglers. Indoors is the asterisk — a scorpion already inside your climate-controlled walls never experiences winter, which is why a January sighting in a bathroom is unusual but not impossible.
Why summer nights are the worst
That is also when they come to you. Bark scorpions hunt the insects drawn to porch lights and climb the warm western-facing block walls at dusk. If your only scorpion checks happen in daylight, you are surveying an empty stage.
Winter clustering: the off-season opportunity
That clustering is exactly why winter sealing matters. From December through February, a large share of a property's scorpions sit concentrated in a handful of spots and barely move. Sealing entry gaps, capping block walls, and treating harborage then works against a stationary target — wait until June and those same scorpions are dispersed across the property and actively hunting.
Hunting with a UV light after dusk
Work the perimeter slowly: block walls and their caps, weep holes at the base of stucco, around pool equipment, the trunks of palms and citrus, and every door threshold. Count what glows and note where. Repeat it two or three nights and you will know whether you have a stray wanderer or a resident population — and where a treatment program should focus.