Keeping Watch Of The Weather

Agricultural meteorology helps farmers through the ups and downs of weather.

by Ed Brotak
PHOTO: Tom Gill/Flickr

Every farmer knows that the weather is a critical factor for crops and livestock. For crops, temperature, sunlight and especially rainfall have major impacts. The growing season is, in fact, the period when temperatures remain above freezing. For livestock, compatible temperatures and adequate water are essential, as well as food, which goes back to growing crops. Most farmers already know something about the weather, but we can go even beyond that if we get into the science of weather and see how it can help the typical farmer.

Past, Present, Future

Meteorology is the science of weather. The aptly named agricultural meteorology, aka agrometeorology, is the application of this science particularly for the production of crops and the raising of livestock. It’s a great example of an applied science, i.e., using scientific knowledge for a specific practical purpose. There are different branches of meteorology encompassing different time frames, all of which provide useful information.

  • Climatology deals with past weather and can provide a framework for what can be expected in the future.
  • The current weather conditions tell you what it is like at this moment.
  •  provides a future prognosis.

For agricultural endeavors, we take a cue from nature. The local plants and animals are suited to a certain environment. In farming, we try to do the same. We choose crops and livestock that can thrive in our particular area, under our particular set of weather conditions. If the weather deviates greatly from the norm, then we can have problems.

Extremes in weather conditions produce the greatest stress and threat. Exceptionally hot or cold temperatures and very wet or very dry conditions would threaten crops and livestock and would need to be dealt with. For example, plant hardiness zones are based on the extreme minimum temperature which can be expected each year in a particular area. Knowing plant temperature tolerances will allow proper crop selection: an avocado tree, native to subtropical southern Mexico, is fine for mild Southern California winters but won’t survive the hard freeze of Minnesota.

Next Year Vs. Next Days

Climatology can tell farmers what is normal, what they can typically expect, especially in terms of temperature and rainfall. It can also tell farmers what types of extremes in weather have occurred in the past, extremes that today’s farmers may well have to face. Current weather conditions can quantify the weather elements, and a farmer can compare them to the current condition of crops and livestock.

If climatology tells us generally what we can expect in the future and thus plan for it, weather forecasting tells us what to expect in the more immediate future and with more specificity. Take frost, for example: Climate data can tell you generally when to expect the last frost in spring and the length of the growing season, which will help you decide what types of crops you can grow and when you can safely plant them. Weather forecasts can be more specific as to when exactly frost will occur but with less preparation time (perhaps a day or two). Then you can take steps to protect tender vegetation with covers, heaters, etc.

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Drought is similar. Climatic records can show typical annual rainfall but also the seasonal variability. It can also show the frequency and severity of droughts in the region. Current data can relate rainfall deficits to what is occurring in the fields. Short-term forecasts can be used to determine irrigation needs. Longer-term outlooks can help in future planning.

Weather Or Not

In terms of climate information, many locations around the country have long-term climate records. From these, the standard 30-year averages or normals are produced for temperature, precipitation, etc. But a closer examination of individual records will show the extremes that have occurred in the past.

The NOAA Center for Weather and Climate Prediction, based in College Park, Md., has tons of statistics in a variety of formats. Information helpful to farmers includes typical dates for the last spring freeze, the first fall freeze, and probabilities of early and late freezes; average length of growing season; and annual precipitation and its seasonal distribution.

In terms of weather forecasts, daily forecasts including temperature and precipitation probability are standard out to seven days. Precipitation amounts are forecast out to 24 hours. Generally, these are very accurate and can be used to determine irrigation needs.

Accuracy does diminish over time, and typically, temperatures are forecast better than precipitation. More general outlooks (not day-by-day) are given out to 14 days with temperature and precipitation forecasts being given as above, below or near normal. These are typically still good and can be used for general farm activity planning. Monthly outlooks go out to one year, but their accuracy is questionable.

There are specific forecasts for frost/freeze conditions with watches given in advance by a day or two and actual warnings at least 12 to 24 hours ahead. This can give farmers time to take protective measures. The National Weather Service is the source of all basic weather information, current and forecast.

How about more specific agricultural weather information? Most states have a state climatologist office, and there are also regional climate centers. Many of these have an agriculture section.

The Southeastern states have Agro­Climate, a website from the Southeast Climate Consortium that provides climate data specifically tailored for the needs of agriculture in this region. Many states have colleges and universities which have agriculture programs, and their websites often include weather and climate information. In addition, states extension services, some associated with colleges or universities, typically include agriculture.

There is a wealth of weather and climate data available for farmers to use. This information can help in planting, frost protection, irrigation and final harvesting. Using weather and climate information wisely may not guarantee success, but it will certainly improve your chances.

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