The weather forecast: producers need to be mindful of heat, ridge-riding storms, flash drought risk and derecho potential through early July and into late summer.
A dangerous early July heat wave is expected to test U.S. corn and soybean crops - as if they have not already been tested enough -- as the growing season moves into a critical period for yield development.
Nutrien agricultural meteorologist Eric Snodgrass says the next two weeks will bring a combination of extreme heat, storm clusters and shifting upper-level weather patterns that growers across the Midwest, northern Plains, Great Lakes and eastern U.S. should watch closely.
The National Weather Service Weather Prediction Center said dangerous heat is building across much of the central and eastern United States, while showers and thunderstorms are expected from the northern Plains into the Upper Midwest and Great Lakes. The agency noted that organized storm development may occur along a frontal boundary as shortwave impulses move through northwest flow.
That setup aligns with Snodgrass’s warning that daily “ridge-riding” thunderstorm complexes may cascade around the northern and western edge of a strong ridge. These storm clusters can bring needed rainfall to some fields, but they may also increase the risk of damaging winds, hail and derecho-type events.
Derechos are long-lived, fast-moving windstorms often associated with organized mesoscale convective systems. According to Snodgrass, historical derecho climatology shows that a corridor through the northern Plains and Upper Midwest carries a greater than 65 per cent annual chance of a derecho-strength mesoscale convective system. He said the region deserves close attention over the next 60 days because northwest flow around the edge of the ridge can support these events.
For farmers, the concern is twofold. Areas that receive repeated storm complexes may see lodging, green snap, hail damage or saturated soils. Areas that miss those storm tracks may face rapid moisture loss under intense heat.
The current national yield projections Snodgrass referenced, made before the heat wave, were 185.6 bushels per acre for corn and 52.5 bushels per acre for soybeans, based on a weekly crop conditions model. Those numbers could become more vulnerable if heat and dryness persist in key production zones.
Heat Builds Into the Fourth of July
The heat wave is expected to intensify up the Mississippi Valley and into the Great Lakes and Northeast, with the peak around the Fourth of July period.
The Weather Prediction Center’s extended discussion described the coming pattern as a “significant, dangerous, and record breaking heat wave” for the central to eastern U.S., supported by a strong ridge anchored over the eastern half of the country.
Snodgrass said heat index values may exceed 110°F in some locations. High soil moisture in parts of the region may add humidity, while warm overnight lows of 75°F or higher could limit crop recovery during the night.
Warm nights matter for corn and soybeans because plants continue to respire after sunset. When overnight temperatures stay high, crops can burn more energy, potentially reducing the efficiency of grain fill later in the season. For livestock operations, high heat and humidity also raise animal health and productivity concerns, particularly where overnight cooling is limited.
The U.S. Climate Prediction Center’s week-two hazards outlook, issued June 28, said extreme heat is likely to continue into the July 6 to July 12 period across many areas of the central and eastern U.S. The outlook also noted that high dew points may push heat index values above 100°F to 105°F in many areas, with warm nights limiting relief.
Flash Drought Risk Bears Watching
Snodgrass identified one of the most important “must watch” regions as the intersection of Iowa, South Dakota, Nebraska and Minnesota.
If ridge-riding storm systems miss this area during the next two weeks, he said flash drought risk could increase and significant yield loss may become more likely.
That risk is especially important because the region includes major corn and soybean production acres. Crops can appear relatively stable early in a hot pattern, but soil moisture can be depleted quickly when temperatures rise, winds increase and rainfall becomes scattered.
Recent drought data show uneven conditions across the country. The U.S. Drought Monitor map released June 25, with data valid June 23, reported favourable soil moisture reserves for most Midwestern summer crops, but also noted variable impacts across the Plains. Drought.gov reported that, as of June 23, 43.74 per cent of the United States and Puerto Rico and 52.33 per cent of the Lower 48 states were in drought.
Snodgrass also pointed to ongoing drought concerns from the Carolinas into the Mid-Atlantic. Although spotty rains have reached some areas, he said sustained rainfall would be needed to remove deeper drought, and that may not happen until later in summer.
Pattern Shift Expected After July 4 to 7
After the July 4 to July 7 window, Snodgrass expects the standing wave pattern to break down and the ridge to retrograde, or shift westward.
By around July 9, the heat centre may move toward the Inner Mountain West, while storms become more active in the lower Mississippi Valley. That does not remove agricultural risk, but it changes where the strongest heat and storm activity may focus.
The CPC week-two outlook also pointed to this westward shift, saying the mid-level high is expected to move westward, bringing some heat relief to parts of the Eastern Seaboard while increasing extreme heat potential across parts of the western U.S.
Snodgrass said growers should also monitor the southern and central Plains in July for a possible flip toward more consistent hot and dry weather. Such a pattern could affect sorghum, cotton, livestock forage, pasture conditions and later-planted crops.
El Niño Becomes the Larger Seasonal Signal
Looking beyond the next two weeks, Snodgrass said strengthening El Niño is the bigger driver as August approaches.
NOAA’s Climate Prediction Center issued an El Niño Advisory on June 11, stating that El Niño conditions are present and expected to strengthen into the Northern Hemisphere winter of 2026-27. NOAA reported a latest weekly Niño-3.4 index value of +0.7°C and said there is a 63 per cent chance of a very strong El Niño during November through January.
For July and August, Snodgrass said an east-based El Niño pattern can favour hot and dry conditions across the South, along with elevated storm risk from the Southwest Monsoon into the northern Plains and Midwest. This “ring of fire” setup can keep storm complexes moving around the edge of a westward- or southward-centred ridge.
Extended models, including GFS 35-day and ECMWF extended guidance, suggest the core of the heat may settle farther south and west later in the summer, while an active Southwest Monsoon develops beneath the ridge. However, Snodgrass cautioned against overreliance on summer precipitation forecasts from broad global models.
Model Caution for Summer Forecasts
Snodgrass emphasized that global models such as the ECMWF and GFS are often weakest during summer because of their coarse resolution and limited ability to resolve convection.
That is especially important for farmers using weather outlooks to make decisions about spraying, irrigation, hay cutting, fungicide timing or livestock heat management. Summer rainfall can be highly localized. One farm may receive two inches from a thunderstorm complex, while another nearby farm receives very little.
For short-term storm tracking, Snodgrass said higher-resolution models such as the HRRR can provide more useful guidance. For larger-scale anomalies, ensembles remain valuable, but he said producers should be very careful when interpreting model forecasts for total precipitation.
Bottom Line for Farmers
The early July pattern brings several agricultural risks at once: dangerous heat, warm nights, severe storm potential and widening dry pockets.
The greatest near-term concerns are in the Midwest, Great Lakes, northern Plains and Northeast, where the heat wave and storm corridor may overlap. After the holiday period, the ridge is expected to move westward, shifting the heat focus toward the Interior West while storm complexes continue through parts of the Mississippi Valley.
For corn and soybean producers, the next two weeks could be important for protecting yield potential. Fields that miss timely rainfall may face increasing stress, while fields under repeated storm tracks may face wind, hail or flooding damage.
Snodgrass’s message is clear: do not focus only on broad rainfall maps. Watch the storm tracks, monitor soil moisture, prepare for heat stress and pay close attention to how the ridge evolves through July.
Photo Credit: NOAA