A warm, sunny, late afternoon might seem like prime time to apply one of the new dicamba formulations, but that wouldn’t necessarily be the case.

An application then could result in damaging, long-distance movement caused by a temperature inversion.

A temperature inversion occurs when warm air, which is light, rises upward into the atmosphere, and cool air, which is heavy, settles near the ground. When warm air hangs above cool air, the two won’t mix. So if you’ve made a dicamba application (some other pesticides are also affected), spray droplets are unlikely to disperse. Instead, they’ll stay bunched in a concentrated mass, and even slight airflow could move them off-target.

Temperature inversions often occur between 5 p.m. and 7 p.m. Tell-tale signs are dust or fog hanging over a road or field. They typically break up at sunrise with increased wind (above 3 mph) or as surface air warms (3°F increase from the morning low).