Climate and Agriculture in the Southeast

A look back at 2017 and the outlook for 2018

A few of you have asked for a summary of the 2017 climate and a peek into what is likely to be ahead for the 2018 growing season. While I don’t have a crystal ball to give definitive answers, I can at least look into the haze and tell you what I think might happen. If you don’t want to read all the text but just want the outlook, skip down to the end for the bottom line.

First, a look back at 2017. For most of the Southeast it was one of the warmest years on record; in Georgia it was the warmest year recorded since 1895, when reliable records first became available.  The months that were most above normal were generally in the non-growing season, including both the early months of the year and late fall. Even March was above normal at many locations in spite of the crippling frost that hit in mid-month. That demonstrates that weather (which drives frost events) and climate (which is described by average conditions) are not the same thing. During the summer, temperatures were milder and even slightly below normal, with July being the only month with considerably above-normal temperatures. The warm average temperatures were more due to night-time heat rather than unusual daytime warmth. In fact, there were no days at official weather stations in Georgia that reached 100 F in 2017. For the April through September growing season, temperatures were only a degree or two above normal at most locations.

Precipitation amounts varied quite a bit across the region both in time and in space in 2017. After a very wet January, the months of February and March were quite dry. This lack of rainfall contributed to problems with soil moisture and planting early in the growing season when some crops were getting established. Most of the months in the growing season had reasonable amounts of rain, although there was some variation in time and space across the region. The year ended with a dry November and December; those dry conditions helped farmers harvest their summer crops but hurt others who were trying to establish pastures or winter grains. Spatially, the coastal plain was the driest part of the state, which may explain why drought has developed most extensively there in 2018.

The impact of tropical storms on Georgia in 2017 was mixed. Tropical Storm Cindy, Hurricane Harvey, and Hurricane Nate brought mostly beneficial rain to the state in mid-June, early September, and mid-October, respectively. Hurricane Irma caused much more significant damage to crops and infrastructure as the storm pushed northward up the Florida peninsula and into southwest Georgia, slowly weakening during that time. In addition to the rain from the storm, high winds associated with the storm caused significant damage to crops such as pecans and cotton, although other crops were less affected. Power outages lasted in some locations for a week or longer due to flying debris and uprooted trees. Storm surge along the Georgia coast led to significant evacuations and caused some erosion and damage to coastal structures.

The moderate temperatures and fairly moist conditions in the growing season did contribute to some problems with pests and fungal diseases that were not seen in the previous two years.  The warm winter in particular allowed whiteflies and other pests to survive during what is usually cold conditions and multiply rapidly once the temperatures warmed up. Army worms were seen in some of the areas that were driest.

Looking ahead to 2018, we are currently in a weak La Niña, the second year of a “double-dip” with a stronger La Niña that occurred last winter.  Typically La Niña brings warmer and drier conditions to the Southeast in winter, especially in southern Georgia and Alabama and Florida. This year the La Niña is fairly weak, allowing very cold air to move south from the Arctic across the eastern half of the US. This has caused problems with cold damage to fruit trees, although it has also provided plenty of chill hours compared to the last two mild years. Most of the Southeast has also been very dry until the last few days, leading to the expansion of drought conditions across the region. This has caused problems for the growth of winter grains and pastures in some areas and has dropped stream levels across the region. The last few days have seen some welcome rains which should halt the spread of drought for now and may reduce it in some places. Wet conditions are expected for the next couple of weeks as storms pass through the area every few days, but drier conditions are likely to return after that.

The current forecast for the next few months is dominated by the likely end of the La Niña over the next few months and the return to neutral conditions. Warmer and drier than normal weather is still considered the most likely to occur over the next few months, although this year I would not be surprised to see more cold outbreak come through the region yet this winter and early spring. If one of those cold outbreaks occurs after a few warm weeks, that could cause problems for fruit farmers, since with ample chill hours this year the trees are ready to bloom. One benefit from the cold should be a reduction in pest pressure going into the next growing season, since populations of whiteflies and other critters should have been knocked back by the frigid weather.

Longer-term, temperature trends since about 1970 are pushing us towards warmer conditions. In that time both the annual average temperature and the April-September temperature have risen about 2°F. Night-time temperatures are rising more quickly than daytime temps. If we have a drought, the likelihood of above-normal temperatures goes up because most of the sun’s energy goes into heating the ground and the air above it rather than into evaporating moisture.

From a precipitation standpoint, recent research (posted on the blog yesterday) indicates that in the second year of a “double-dip” La Niña, drought is more likely to occur in the Southeast than in the previous year. The strongest signal for this is in the Tennessee Valley, which would include northern Georgia and Alabama as well as points north. We also know that in La Niña or neutral years, the Atlantic tropical season tends to have more storms than the long-term average, which could mean more rainfall for those areas along the paths of whatever storms develop. However, we cannot predict the storm paths before the storms form, so that does not provide much guidance for general conditions during the growing season. If you have access to irrigation water, drought is not necessarily a bad thing, since low humidity reduces the incidence of fungal diseases, which could lead to a reduction in the number of applications of chemical sprays. If you depend on rain for your crops, though, it has the potential to be a rough year.

Looking farther down the road, it is unlikely (although not impossible) that we will go into a third winter of La Niña. Much more likely is the possibility that we will swing into the opposite phase, El Niño, instead. That would mean next winter is likely to be cloudier, cooler and wetter than average. We won’t know until around August if that is likely, though, so for now you should just be aware of the possibility it might happen.

Bottom line for this coming growing season:

  • Current dry conditions should be alleviated somewhat in the next few weeks but are expected to return later this spring.
  • Drought is more likely than usual this summer, especially in the Tennessee Valley area.
  • Average temperature continues to rise, making warmer temperatures more likely, especially if we are in drought. Next summer is likely to be hotter than last year, which means heat stress on crops and livestock will be more of an issue this year.
  • The Atlantic Ocean basin will probably have another active year, but at this point we can’t say where the storms will go or what damage they are likely to cause. You should be prepared for damage and power outages every year, regardless of whether they come from hurricanes, ice storms or severe thunderstorms.