Monitoring Precipitation and Drought

Tracking cumulative plant-year precipitation allows managers to determine when forage deficits are likely to occur.

You may be interested in tracking weather not only in your region, but also in near-by regions where you may be able to ship livestock or purchase feed.

One of the best things you can do is invest in some quality rain gauges and start tracking your own precipitation. In addition, here are some websites that monitor precipitation and drought indices.

Weekly, Monthly and Plant-year Precipitation

Current Drought Status

	U.S. Drought Monitor Provides a weekly assessment of drought conditions for the U.S., with categories linked to possible impacts. The U.S. Drought Monitor is updated each Thursday morning.
	Standard Precipitation Index (SPI) Shows the actual precipitation compared to the probability of precipitation for various time frames. A drought event occurs any time the SPI is continuously negative and reaches an intensity of -1.0 or less. The event ends when the SPI becomes positive.
	VegDRI VegDRI maps are produced every two weeks and provide regional to sub-county scale information of drought's effects on vegetation.

Short and Long Term Forecasts

	National Weather Service Climate Prediction Center Forecasts temperature and precipitation at various time scales out to a year. Useful in shorter time scales for planning hay cutting, etc.
	U.S. Seasonal Drought Outlook National map combines information of current forecasts and drought conditions to predict changes in the Drought Monitor depiction.

 How to Use Precipitation Data

Stocking rates are based on average rainfall. If less-than-average rainfall is received before and during the rapid-growth windows of key forage species, there will likely not be enough forage to carry the entire herd through the grazing season without negative effects on the vegetation.

Monitor precipitation levels at the midpoint of rapid-growth windows for dominant cool-season and dominant warm-season grasses.

• Drought management plans for semiarid regions should be implemented when cumulative plant-year precipitation is 20 to 25% below average.
• Livestock producers in subhumid regions may choose to act when precipitation deficits reach 30 to 35%, because of relatively high yield responses to precipitation.  

Plant-year precipitation is measured starting in October to reflect moisture accumulation or deficits experienced over the winter months.