Summertime Climate After An El Niño Winter

By Laura Edwards

El Niño is here to stay… at least through the winter season. It is one of the primary drivers of our climate that affects us on a multi-year scale in North America. In South Dakota, very strong El Niño conditions, like we have this year, usually mean warmer than average conditions in the winter season. But what happens in the growing season following an El Niño winter? As fall harvest season is upon us, it will soon be time to make some early seed and chemical purchasing decisions for the 2016 crop year, and perhaps some information about those summer seasons will help inform those decisions.

A Historically Strong El Niño

The current El Niño, as determined by sea surface temperatures in the Pacific Ocean, is ranking as number two or three among the strongest El Niños since 1950. The comparable years are 1982-83 and 1997-98. Here we consider the May through September growing season following these two El Niño winters. In general, very strong El Niños tend to dissipate quickly. This limited size of just two growing seasons, combined with other variables creates some uncertainty in the summer season forecast.

Impact on Summer Climate

In both summers of 1983 and 1998, warmer than average conditions affected eastern South Dakota, with the largest temperature anomalies centered on Iowa.

Differences arose in the precipitation for each season. In 1983, near average or wet conditions occurred statewide during the spring season. Then dry conditions prevailed most of the summer, during July, August and September. At any given time in the 1983 growing season, there was some level of minor to moderate drought conditions somewhere in the state. In 1998, June and July were notably wet in western/southwestern South Dakota, though the entire growing season ended up above average for rainfall in those areas. July 1998 had some short-term drought in the northern tier counties, and then September was exceptionally dry and warm.

Summer 2016 Outlook

It is too early to tell for sure what summer 2016 will bring, but after looking at two recent summers following strong El Niños, it may be best to be prepared for some amount of warm and dry conditions. The East River counties tend to be more susceptible to drought during summers like these than the western half of the state.

Figure 1. May through September 1983 precipitation departure from normal. There were some wetter months during the growing season, but overall rainfall was 70 to 90 percent of average in the many parts of South Dakota.