I have done both ground water locating and facade & roof inspection with thermal. If you're to spot groundwater, cooler times of day—like early morning or late evening—are your best bet. After a chilly night, moist areas in the ground tend to hold onto heat longer than dry spots, so they’ll show up warmer on your thermal feed. You’ll get better contrast and clearer results when the surrounding soil has cooled down but the water hasn’t, making it easier to pick out those hidden wet zones. For roof and facade leak detection, warmer ambient temps work in your favor. Late afternoon is ideal, especially after a sunny day, because building materials heat up and any moisture trapped inside will behave differently thermally. Wet insulation or leaks might show up as cooler or warmer patches depending on the material, and that contrast is what helps you spot trouble. Obviously you'll want to avoid scanning after rain—everything’s wet and the readings won’t tell you much.
