How to Use


The National Cattle Comfort Index Maps include:

- Cattle Comfort Index at 100% sunlight under cloudless conditions

- Cattle Comfort Index at 60% sunlight under partially cloudy conditions

- Cattle Comfort Index at 20% sunlight under overcast conditions

Choose the sunlight level that is closest to your sky conditions. In the summer, it is best to err on the high side, because sunlight increases heat stress. In the winter, since cold stress is of more concern, it is better to err on the low side. Sunlight reduces cold stress.

All sunlight levels are equal at night, since sunlight is zero and has no positive or negative impact.

Best choice 100% sunlight

Sky with 90 percent blue and 10 percent puffy, cumulus clouds.

Best choice 60% sunlight

Sky filled with high clouds. Diffuse bright sunlight.


Best choice 20% sunlight

Heavy overcast with dark storm clouds.


All maps times are in Eastern Time.

Maps are updated hourly on the hour from National Weather Service METAR data. The Oklahoma Mesonet does not quality assure National Weather Service METAR data. METAR weather stations are located at airports across the nation. Airports tend to be at lower elevations, where conditions tend to be hotter in the summer and not as cold in winter compared to higher elevations in nearby mountains. The National Cattle Comfort maps do not show cattle comfort index differences due to elevation differences between METAR weather station locations.

These maps allow the calculation of cattle comfort levels under three different sunlight levels across the nation. These three maps compensate for the lack of a national database of solar radiation. Users will have to determine which is the best map for their location and cloud cover. The three sunlight level maps are produced hourly, so that cattle producers can change which percent sunlight they need to use as their cloud conditions change through the day. Maps are equal at night, because sunlight is no longer a factor in cattle comfort index calculation.

National Cattle Comfort index at 100% sunlight will provide the highest estimate of daytime cattle heat stress during summer months. For cold stress, the National Cattle Comfort index at 20% sunlight will provide the lowest estimate of daytime cattle cold stress during the winter months.


What do the Numbers Mean?

National Cattle Comfort Index values are reported as degrees Fahrenheit. The values do not represent exact temperatures. They do represent the approximate hot and cold levels an animal is being exposed to and is dealing with physiologically.

Heat and cold stress level categories for the Cattle Comfort Advisor are:

Mesonet Cattle Comfort Categories  Cattle Comfort Index °F  Impacts
 Heat Danger >105 Animal deaths may exceed 5%
 Heat Caution >85 Decreased production, 20% or more. Reduced conception, as low as 0%
Comfortable 15 to 85  
Cold Caution <15 to -20 18-36% increase in dry animal feed
Cold Danger <-20  


The heat and cold stress categories have been set for weaned, healthy, adapted cattle. Younger animals, animals new to an area, or animals weak from disease or insects will have experience heat stress at lower National Cattle Comfort index values and cold stress at higher National Cattle Comfort index values.

The National Cattle Comfort index categories will vary for different breeds, depending on breed tolerance to heat or cold conditions. The National Cattle Comfort index assumes animals have developed a hair coat suitable to their current environment and time of year. 

The National Cattle Comfort index is not factored for wet, soaked hair coat. Extra pre-cautions need to be considered when animals are exposed to soaking rain prior to cold conditions.

Heat and cold stress are cumulative. Animals exposed to heat or cold extremes can recover quickly when stress is short-term and comfortable conditions return. An example would be a daytime peak of 112 followed by a nighttime minimum of 68. 

Daytime highs above 105 and nighttime lows above 75 for multiple days, do not allow cattle to dissipate heat from the environment and digestion. In such conditions, animals should be carefully monitored for heat stress symptoms and appropriate mitigating measures implemented.


Handling Heat

Heat stress can reduce productivity in beef cattle herds. Severe heat stress can reduce reproductive performance and/or daily weight gain. Cattle are more sensitive to heat stress than humans. The National Cattle Comfort Advisor heat stress is a combination of air temperature, relative humidity, solar radiation and wind speed. Animal age, hair coat length, hair coat color, and nutritional status interact with environmental factors to impact severity of heat stress on individual animals.

Provide ample water

The most important management concern in heat stress situations is to provide ample water. Cattle will drink more water when the water is cleaner and cooler. Provide enough tanks for cattle to be able to get the water they need. If possible, water should be cooled. Tanks should be cleaned weekly to encourage water consumption. Making water available under shade will increase water consumption.

On days when the cattle comfort index reaches 85ºF or higher, cattle commonly need 2 gallons of water per 100 pounds of body weight.

Avoid handling cattle

Handling cattle can elevate their body temperature by as much as 3.5ºF. If cattle must be worked on days when the National Cattle Comfort Index is likely to go over 85ºF, try to do the work before 8:00 AM and keep the maximum time in the holding facilities to 30 minutes or less. On days when the index will be 85ºF or above, do not work cattle after 10:00 AM.

Change feeding patterns

For fed cattle, shift the feeding schedule toward evening on days when the National Cattle Comfort index is above 85ºF. Try to deliver 70% of the daily scheduled feed two to four hours after the peak National Cattle Comfort index value. Small amounts of feed during the heat of the day, keeps metabolic heat of digestion low.

Provide shade

A shade tree is just as welcome a relief for cattle as humans on a hot summer day. Shade can also be constructed. Shade height should be 8-14 feet tall and should be large enough to provide 20-40 square feet per animal. The most effective shade is a solid reflective roof constructed of white colored, galvanized, or aluminum materials. Shading with wooden slats, plastic fencing, or other materials that allow flecks of sunlight to hit the animals are less effective. If possible two shaded areas are recommended, one over the feed area to increase feeding time, and another away from the feed area to encourage the cattle to rest. Water should be made available under both shaded areas, to increase the water consumption during heat stress period. If the structure is left up year-round, construct a frame adequate for snow load. Shade is insurance against mortality loss. Any performance benefits are a bonus.

Improve airflow

Consider where the cattle are located and if there is any air restriction. Buildings, high fences, or vegetation can block airflow. A 6-foot high windbreak can obstruct airflow for 60 feet downwind.

Control biting flies

Stable flies cause cattle to bunch and disrupt cooling. Monitor the situation and control the flies as needed. Eliminate any shallow pools or muddy areas nearby, since they are common breeding areas for flies.

Wetting animals

In emergency heat stress situations, it may be necessary to cool cattle by soaking them with water. A sprinkler or water nozzle needs to have enough pressure and water volume to wet the animal to the skin. Mists that only wet an animal’s outer hair coat may actually increase heat stress by increasing the nearby relative humidity. Local fire departments may be able and willing to soak cattle down in an extreme emergency situation.


Coping with Cold

Beef cattle can be comfortable within a wide range of temperatures, depending largely on hair coat length and hair coat condition (dry, wet, muddy etc.). The National Cattle Comfort maps provide a tool that livestock producers can use to monitor cold stress conditions. It assumes animals have a hair coat length and condition suitable for their location and season.


In general, a cow’s energy requirements increase 1% for each degree the cattle comfort index is below 32°F. For a cow wet to the skin, the increased energy requirement begins at 59°F and increases 2% for each degree drop.

In cold wet conditions, this increased energy need is often virtually impossible to accomplish with feedstuffs available on ranches. In addition, this amount of energy change in the diet of cows accustomed to a high roughage diet, must be made very gradually to avoid severe digestive disorders. Therefore, the more common-sense approach is a smaller increase in energy fed during wet cold weather and extending the increase into more pleasant weather to help regain energy lost during the storm.

For example, a cow consuming 16 pounds of grass hay per day and 5 pounds of 20% range cubes under mild weather, could have its feed increased to 20 pounds of grass hay per day (also possibly offering a better quality hay) plus 6 to 7 pounds of range cubes during a severe weather event. This is not a doubling of the energy intake but extending this amount for a day or two after a storm may help overcome the energy loss during the storm and is done in a manner that does not cause digestive disorders.

A second approach that is often used is to reserve the highest quality hay for feeding during stressful weather periods.


Windbreaks are valuable to reduce wind speed and reduce blowing snow. This will reduce animal cold stress and nutritional demand. Windbreaks are created for general wind direction They may not be fully effective when storms produce wind or blowing snow from an untypical direction for the location or season.



- T.L. Mader, L.J. Johnson, and J.B. Gaughan. A comprehensive index for assessing environmental stress in animals. Journal of Animal Science 2010, 88(6):2153-2165. Erratum, Journal of Animal Science 2011, 89(9):2955.

- Managing Feedlot Heat Stress, Nebraska Extension NebGuide, G1409, Revised September 2007.