When to use
- Before riding or trailering during summer months
- Planning outdoor exercise schedules for horses
- Assessing whether to cancel or modify equestrian events
- Monitoring conditions at boarding facilities
ToolsConductScience tool
Temp + Humidity IndexFree in-browser calculator
Heat Stress Risk Calculator.
Is it too hot to ride? Enter temperature and humidity to assess equine heat stress risk and get an action plan.
PrivateData stays in your browser
LiveNo sign-up required
Validated2026-04-08
CitableMethods and citation included
Calculator
Results update in placeTry it out
Load example heat stress risk calculator data to see the full workflow
Environmental Conditions
Heat Stress Assessment
Risk Level
Moderate Risk — Reduce Work
Cooling efficiency: Decreasing
THI Value145
0130150180250
Recommended Actions
- Reduce work intensity and duration.
- Provide access to shade and fans.
- Offer water every 15–20 minutes during work.
- Monitor for signs of overheating (excessive sweating, flared nostrils).
Based on UConn Extension equine heat stress guidance. This tool provides environmental risk assessment for management decisions. If your horse shows signs of heat stroke, call your veterinarian immediately.
Do not use for
- As a substitute for veterinary assessment when a horse shows signs of heat stroke
- For species other than equines — thresholds are horse-specific
THI is the sum of temperature (°F) and humidity (%)
THI = Ambient Temperature (°F) + Relative Humidity (%). Below 130 is low risk, 130–150 moderate, 150–180 high, above 180 extreme. Hard work bumps risk up one level in the moderate zone.
Watch for cessation of sweating
Anhidrosis (failure to sweat) is more dangerous than excessive sweating. If a horse suddenly stops sweating in hot conditions, this is a veterinary emergency.
Shade reduces effective heat load by 10–15°F
Without shade, a horse in the moderate-risk zone may effectively be in the high-risk zone. Always factor in shade availability.
1
Method
Computes the Temperature-Humidity Index (THI = ambient temp °F + relative humidity %). Categories: <130 low risk, 130–150 moderate, 150–180 high, >180 extreme. Activity level and shade adjust risk. Based on UConn Extension equine heat stress guidance.
2
Validated
Last validated 2026-04-08. Calculations are designed for planning and documentation support; verify procurement decisions against manufacturer specifications or institutional SOPs.
3
How to cite
How to Cite
ConductScience Equine Heat Stress Risk Calculator (v1.0). ConductScience, Inc. 2026. Available at: https://conductscience.com/tools/heat-stress-risk-calculator
UConn Extension. Equine Heat Stress Guidelines. University of Connecticut.
Equine Thermoregulation
Horses generate significant metabolic heat during exercise and rely primarily on evaporative cooling (sweating) to thermoregulate. When humidity is high, sweat does not evaporate efficiently, and the horse’s core temperature can rise rapidly. Unlike humans, horses have a large muscle mass relative to surface area, making heat dissipation more challenging. The THI captures this relationship: even moderate temperatures become dangerous when humidity is high.
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