Considering thermography to evaluate a horse’s legs? Better move that patient inside and shut the doors. Austrian researchers recently learned that wind and air drafts can affect themographic readings of horses’ front legs—very quickly, in fact—potentially leading to false positive or negative results.

“I was surprised at how fast the temperature decreased after the onset of airflow,” said Simone Westermann, DrMedVet, a researcher in the Units of Large Animal Surgery and Orthopaedics at the University of Veterinary Medicine in Vienna. Westermann and her fellow University of Veterinary Medicine researchers studied the effects of air, angles, distances, and natural temperature differences on multiple thermographic readings of 16 healthy adult horses.

Slight drafts of air—what Westermann called “barely noticeable wind velocities”—caused a reduction in the temperature of horses’ forelimbs, compared to the temperature recorded without drafts, she said. A gentle breeze of only two meters per second could make leg temperatures drop as much as 1.5°C (2.7°F) in as few as one to three minutes.

Temperature can also naturally vary slightly from one forelimb to the other in a healthy horse, according to Westermann’s research, so those evaluating thermographic readings should take into consideration the possibility of natural differences between legs