A remote pilot arrives at a shoot at 10 AM. Surface visibility appears clear for several miles horizontally. However, looking toward their 350-foot planned altitude, the sky appears hazy and milky above approximately 200 feet. This visual effect is most likely caused by:

Why →A temperature inversion occurs when a layer of warm air sits above cooler surface air, creating a stable lid that traps particulates, humidity, and pollutants in the lower layer. This produces a visible haze band at the inversion height. From the ground, horizontal visibility may appear acceptable, but the haze layer significantly reduces visibility at and above the inversion altitude.

The trap →Surface fog sits at ground level and burns off upward; it cannot leave a haze band at 200 feet over already-clear ground. Cumulus bases read as distinct layers, not diffuse milkiness.

Field note →If a haze layer reduces your ability to see and maintain aircraft orientation at your planned altitude, that is a VLOS and visibility go/no-go factor. The 3 SM visibility minimum applies to your actual flight environment, not just surface conditions.