Desert Climate: Hot Days, Cold Nights, and Relentless Dryness

Deserts are defined by aridity—typically under 250 mm (10 inches) of annual precipitation—not temperature. But the classic "hot desert" (Sahara, Mojave, Arabian) delivers extremes:

• Daytime heat: 40–50°C (104–122°F) common; ground temperatures can exceed 70°C (158°F)
• Nighttime plunge: Clear skies and bone-dry air allow rapid radiative cooling—drops of 20–30°C (36–54°F) overnight
• Humidity: Often below 10%; evaporation far exceeds precipitation
• Wind: Unobstructed flow across open terrain generates sustained winds; dust storms (haboobs) can exceed 100 km/h (60 mph)

Cold deserts (Gobi, Great Basin, Patagonia) follow the same aridity rule but with freezing winters. All deserts share sparse vegetation, specialized fauna, and fragile soils easily disrupted by human activity.