Here Comes the Sun: Summer Weather Forecast

Summer has arrived in the Midwest. Farmers are reporting good emergence, which means planting happened on time and crops are off to a great start in most areas. The outlook is looking up for a majority of the U.S. Corn Belt — with a few notable exceptions. The Dakotas (especially North Dakota), and then a swath extending eastward all the way to Michigan, are entering summer with a deficit of moisture and increasing concerns of drought. In the South, some of you had too much rainfall. But all in all, it is a time for optimism. As for the summer, what weather should U.S. farmers expect?   

El Niño and La Niña Are Taking a Break

Not literally of course, but the conditions in the tropical Pacific Ocean will not have a great deal of influence over summer weather on your farm. Local conditions can be more helpful in predicting what July, August and September will hold for U.S. corn and soy farmers. 

The Novel Nature of Midwest Summers

The U.S. Corn Belt is unique in many ways. In terms of weather, the month-to-month correlation in the summer is surprisingly strong. What do I mean by correlation? Put simply, if it is hot and dry in May, it is likely that June, and possibly July will also be hot and dry. Likewise, a hot and dry July is more likely to be followed by a hot and dry August. This is especially so in the Central Great Plains and Midwest states. Similarly, cool and wet months are more likely to be followed by another cool and wet month.

As a scientist, I always discourage people from drawing conclusions based on anecdotes. But in this rare instance, what you experience in your fields this spring and early summer can offer a window into future weather patterns. Why? Because moisture and heat are like a ball rolling down a hill. Once they get going, they can be hard to stop. What can stop it? A change in the large scale pattern and a shift in the jet stream across North America. 

Connecting Crop Water - Use and Weather

Why does drought persist? Let us begin with something very simple. Crops extract water from the soil and put it back into the atmosphere. Once back in the atmosphere, the moisture helps produce clouds and rain showers and returns the water to the soil. This process repeats...unless the cycle is broken and the soil is too dry. Low-moisture content in the soil means less evaporation, which leads to less rainfall. The incoming solar energy is then converted to heat (rather than evaporation), which further dries out the soil. The momentum continues—keeping things hot and dry. This is partly why overcoming drought can be an uphill battle.

Summer Weather Forecast

Northern Drought Will Continue

For the next two months, the drought will persist in North Dakota and Minnesota. It may also expand south from North Dakota and southeast into Northwest Iowa. Moving east, there is a chance the drought conditions may ease in July and August. 

As you begin to plan your scouting and other growing season activities, you might wonder how your fields have performed in the past under similar weather conditions. If you log into Climate.com, you can pick a date range and look back five, 10, even 20 years. Find a season when you had a similar amount of rainfall and compare that to yield data. I am confident that you will see patterns, even some you hadn’t noticed before, that will help forecast what to expect at harvest. 

Dry In the West, Wet In the East

The jet stream this summer is expected to flow primarily west to east across the Northern U.S., which will keep the western part of the plains hotter and drier than normal. If you’re farming in those regions, I would expect that trend to continue into August. As I said earlier, a special shoutout for farmers in the Dakotas who had a tough spring and are headed for a challenging summer. But in general, the farther east you move into the U.S. Corn Belt, the more moisture you will find in the atmosphere this summer. 

Why NOAA Seasonal Forecasts May Look Different

While we’re discussing forecasts, I thought I would give you a behind-the-scenes update from our friends at NOAA. They recently updated the long-term normals (a 30-year record). Why should you be excited? Because NOAA only updates the data in 10-year increments. That means that last year, they were basing their forecasts on an older set of data. Now, we have jumped another decade, which will help the long range forecasts better account for climate change, and as a result will likely be more accurate in the coming years. 

Good luck this growing season. In all, there is a lot to feel good about heading into these hot months of July and August. Across the Corn Belt, farmers are looking up and feeling optimistic about the summer. I hope you can count yourself among them.