• Definition & Media Coverage
  • "Corn sweat" is simply a catchy term for evapotranspiration
  • Justin Glisan was interviewed by major news outlets (Washington Post, CNN, USA Today, CBS)
  • The phenomenon was trending during the hottest week of July 2025 during a heat dome
• Scientific Reality
  • Corn releases water vapor and oxygen through transpiration (not actually "sweating")
  • Adds 3-5% to relative humidity locally (3-5 degrees to dew point)
  • Peak evapotranspiration occurs during corn pollination/tasseling season
  • Iowa has 13 million acres of corn contributing to this effect
• Comparative Analysis
  • Prairie grasses actually have slightly higher evapotranspiration rates than corn
  • Corn and soybeans have very similar ET rates during peak growth
  • Historical prairie landscape would have different hydrology and soil structure
  • Modeling is used to understand these complex comparisons since full-scale experiments aren't feasible
• Weather Forecasting History
  • First tornado warning issued in 1940s by Miller and Fawbush at Air Force base
  • WWII and 1946 weather radar development improved forecasting capabilities
  • 1925 Tri-State tornado killed ~700 people despite warning signs, but no communication system existed
  • Modern forecasting balances accuracy with avoiding "boy who cried wolf" scenario
• Social Media & Public Education
  • Madelynn Wuestenberg urges people to stop sharing corn sweat TikToks
  • Working on program to fact-check weather-related social media content
  • Emphasizes need for agricultural meteorologists with both meteorology and agronomy backgrounds

Summary generated by Claude.ai

• Iowa Weather History:

  • On July 3, 2001, severe thunderstorms in southern Iowa produced very large hail: 2.5-inch stones at Osceola, 3-inch at Otley, and 4-inch at Truro, causing widespread and extensive damage.

• Recent Severe Weather Trends:

  • Hail has been infrequent this year, with the most recent notable event in north central/northwestern Iowa a few weeks ago.

  • The primary severe weather mode this season has been wind, with only a few pockets of hail and very few tornadoes (no tornadoes in May, five reports in June, including a landspout).

  • Despite fewer severe storms, thunderstorms have provided good rainfall, especially in northern and western Iowa, aiding drought improvement.

• 7-Day Weather Forecast:

  • Expect average summer weather: several chances for thunderstorms over the next week.

  • Temperatures will be typical for the season, with daytime highs in the mid-80s and overnight lows in the mid to upper 60s.

  • Rainfall (QPF) is forecast at 0.5 to 1 inch, mostly thunderstorm-driven and variable.

  • The best chance for statewide rain is Saturday night into Sunday, with additional chances late Tuesday into Wednesday.

• Climate Outlook:

  • The July outlook initially showed a large dry area from the High Plains to the Gulf, but recent wet weather reduced this to a small bullseye over Nebraska, Kansas, Missouri, and Iowa.

  • The last ten years of Julys in Iowa have been 5–10% drier than average, influencing the forecast.

  • The first half of July still leans wet for most of Iowa; models suggest the second half could turn drier.

• Past Week’s Weather:

  • The past week was about 2°F above average for temperatures and below average for rainfall.

  • The state is transitioning to a quieter storm track, and soil moisture has improved thanks to late June rains.

  • Eastern Iowa, especially around Waterloo, Cedar Rapids, Washington, Wapello, Linn, and Black Hawk counties, remains drier and needs more rain.

• Specialty Crop Impacts:

  • Zucchini: Squash vine borer is active and affecting small plantings; some growers report a lull in fruit set, possibly due to poor pollination (weather or varietal timing).

  • Squash bugs: Adults are mating; now is the time to scout for eggs and treat nymphs with insecticidal soap or oils. Adults are hard to control; many growers opt to replant rather than spray.

  • Japanese beetles: Now appearing, mostly affecting basil (culinary and cut flower types), zinnias, and grape leaves.

  • Basil downy mildew: 'Cardinal' basil (popular for cut flowers) lacks resistance and is vulnerable. 'Thai Prospera' basil offers downy mildew resistance and may be a better filler for bouquets.

  • Garlic: Harvest is beginning. Use the "five green leaves, sixth browning" rule to time harvest for optimal bulb quality and storage.

  • Tomato spotted wilt virus: A grower in Kalona who lost most of his tomato crop to this virus in previous years now sees minimal infection, likely due to reduced thrips pressure. Onion thrips can also vector the virus, so monitor onions for thrips damage.

• Upcoming Resources and Events:

  • Dan will share links in the newsletter on strawberry plug planting, spring broccoli variety trials, root maggot information, and upcoming field days (flower field day in Decorah, urban ag field day in Waterloo, and a native plant propagation survey).

summary generated using Perplexity.ai

• Iowa Weather History:

  • On June 19, 1996, severe thunderstorms produced very large hail in northwest Iowa, with a 3.5-inch stone near Hinton (Plymouth County) and a 4.5-inch stone at Cushing (Woodbury County), causing $200,000 in damage to vehicles and buildings.

• 7-Day Weather Forecast:

  • Iowa is entering a "blast furnace" pattern: temperatures will soar 15–20°F above average, with highs in the 90s to upper 90s and overnight lows in the mid to upper 70s.

  • Persistent high overnight lows will make it difficult for people and plants to recover.

  • Strong southwesterly winds will continue, bringing high dew points and Gulf moisture.

  • By days 4–6 (early next week), the northwestern two-thirds of Iowa could see 2–5 inches of rain, especially in western Iowa, which needs relief from drought.

• Climate Outlook:

  • The 6–10 day forecast shows the heat shifting east, with a tighter temperature gradient and continued potential for heavy rainfall, especially in northern Iowa.

  • The 8–14 day outlook keeps a warm and wet signal, which is positive for the wettest month of the year after recent dryness.

  • The 3–4 week outlook still leans warm, with no clear signal on rainfall.

  • The initial July outlook (issued June 19) leans slightly warm statewide, with a slight lean dry in the western third of Iowa.

• Recent Weather and Notables:

  • The past week was slightly warmer than average with an unsettled pattern of pulse and “popcorn” thunderstorms across the state.

  • Severe weather ingredients did not come together for widespread severe storms, but there was a landspout tornado in eastern Iowa.

  • Landspouts are weaker, photogenic tornadoes (a step above dust devils), typically anticyclonic, and distinct from stronger tornadoes.

• Specialty Crop Impacts:

  • Hot weather is negatively affecting broccoli development, leading to issues like “brown bead” (brown florets) and heat-delayed buds.

    • Brown bead can be caused by hot, humid nights; broccolini is less susceptible and can regrow after harvest.

    • Hollow stem in broccoli may result from fast growth due to excess nitrogen and water, not just boron deficiency. Tighter in-row spacing and careful nitrogen management can reduce hollow stem.

    • Boron deficiency causes brown, dead cells lining the hollow stem, while fast growth causes uniformly green or white hollows.

    • Boron should be mixed with other powders for uniform soil application to avoid toxicity.

    • Some broccoli varieties (e.g., Green Magic) are more prone to hollow stem than newer ones (e.g., Eastern Crown).

    • Heat can also cause uneven, lighter green patches in broccoli heads (heat-delayed buds).

    • Brown bead does not grow out, but heat-delayed buds sometimes do

  • Cabbage White butterflies and their caterpillars are active.

    • BT (Bacillus thuringiensis) sprays are effective when caterpillars are first seen, especially on new growth and broccoli heads.

    • Rotate BT with other organic insecticides if resistance is suspected.

    • Cabbage moth caterpillars can hide inside broccoli heads, making washing difficult.

Summary created using Perplexity.ai

June 13, 1976: an F5 tornado near Luther, Iowa, was one of the largest in state history. The tornado, nearly a mile wide, spawned multiple satellite tornadoes and caused widespread destruction between Boone and Ames, demolishing over 60 homes and 300 farm buildings. Charles Barthold’s iconic photographs of the event contributed to tornado science and earned him a Peabody Award.

• Expect continued warmth with a risk of extreme heat in the coming week.

• An active precipitation pattern is forecast, with widespread rain likely. Most of Iowa should receive at least an inch of rain between June 12–19; northern areas may get up to 2 inches, especially with thunderstorms.

• The Climate Prediction Center’s outlooks (6–10 day, 8–14 day, and 3–4 week) all lean toward above-normal temperatures and slightly above-normal precipitation.

• There is a slight risk for extreme heat (June 19–21) and heavy precipitation (June 19–22, especially in northern Iowa).

• The past two weeks were cooler than normal, averaging 65°F (2–4° below normal).

• On June 11, hailstorms hit northern Iowa (Palo Alto, Kossuth, Hancock Counties), causing severe crop damage and total losses in some corn and soybean fields.

• Aster Yellows in Garlic and Other Crops:
  Aster leafhopper infectivity for aster yellows has jumped from near zero to 15–20% in Michigan, exceeding last year’s rates. Growers should watch for symptoms in garlic, flowers, and lettuce. One Iowa garlic grower observed premature yellowing and is testing for the disease; comparison with seed garlic from another location suggests possible infection.

• Squash Yellowing (B Gene):
  Yellow leaves in squash during cool weather may be due to the B gene, which breeders retain for its positive effects (fruit color, yield, virus resistance). The B gene can be identified by a yellow stem on yellow squash.

• Onion Thrips:
  High thrips numbers reported in onions and mulberries. Thrips are tough to control; Dan recommends using azadirachtin (from neem), horticultural oil, a spreader-sticker, soil-drench nematodes, and mycopesticides (Beauveria bassiana). Control is important because thrips damage increases storage rots.

• Aphids:
  Aphids can multiply rapidly, especially under row covers. Dan suggests treating transplants with insecticidal soap (e.g., M-Pede) before planting and repeating the spray after five days. In the field, use water sprays, insecticidal soap, oils, and azadirachtin. Tank-mix treatments after jar testing. Attract beneficial insects with sweet alyssum and other flowers, especially in tunnels or greenhouses.

• Squash Vine Borer:
  The pest is now active in central Iowa. Remove row covers from flowering squash, scout for eggs at the stem base, and use BT sprays or manual removal of larvae. Large fields are less affected; small plantings are at greater risk.

• Tomato Yellow Shoulder Disorder:
  This disorder is more common in hot weather and is linked to potassium deficiency and high fruit temperatures. Dan recommends ensuring adequate potassium and using shade cloth in high tunnels to keep fruit shoulders cool. Some cultivars are more susceptible.

Podcast summary generated using Perplexity.ai