University of Minnesota Extension: Heat stress in dairy cattle
Practical guidance connecting THI with animal observations and management.
Learn more: University of Minnesota Extension: Heat stress in dairy cattleAnimal heat stress · Practical guide
Temperature-humidity index: what it measures and what it cannot tell you
THI combines air temperature and relative humidity into an environmental screening indicator. It supports attention and planning; it does not diagnose an individual animal.
A weather-based signal
Heat exchange becomes more difficult as temperature rises and humidity limits evaporative cooling. THI summarizes those two weather variables so conditions can be compared over time and across locations.
The BGPD Labs analyzer uses modeled outdoor weather for selected coordinates. It separates historical and forecast periods and displays the methodology version returned by the authoritative API.
How to interpret a result
- Read the classification together with the date, local time and duration of exposure.
- Compare forecast signals with current observations at the farm.
- Treat consecutive elevated hours differently from an isolated hourly value.
- Keep the active animal group and methodology version visible when documenting a result.
Important limits
Outdoor modeled weather does not describe conditions inside barns or pens and does not account for shade, airflow, solar radiation, cooling, water access, coat, production level, acclimation or health. Published thresholds also vary with population, formula and context.
Observe animals directly and follow local operational and veterinary protocols. The analyzer is environmental decision support, not veterinary diagnosis or treatment advice.
Sources and further reading
Chang-Fung-Martel et al. (2021)
Global meta-analysis of THI, heat stress and dry-matter intake in cattle.
Learn more: Chang-Fung-Martel et al. (2021)Polsky and von Keyserlingk (2017)
Peer-reviewed review of heat stress and dairy-cattle welfare.
Learn more: Polsky and von Keyserlingk (2017)