August 20th, 2026 Weather Outlook

Key Points

Recent Conditions

• Temperatures were above normal by 2-5°F across nearly all of Wisconsin last week. Growing degree-day accumulation continues to run ahead of normal pace. 
• Most of Wisconsin received precipitation totals of less than 0.5” last week. Southwest Wisconsin received 0.5-2”, and similar totals were noted in parts of the Central Sands. 
• The northwest counties have been very dry over the past 30 days. Several Wisconet stations in this region report 30-day rainfall totals of 0.5” or less. 

Impact

• For Wisconet stations included in the chart and table, changes in soil moisture were a mixed bag. Locations that saw over a half inch experienced gains in soil moisture. 
• Satellite-based soil moisture estimates indicate that dryness in the top 1 meter worsened in the north-central, northwest, and east-central counties over the past week. 
• Drought worsened across northern counties, with an expansion of D2 coverage and the addition of D3 (extreme) drought in the Northwoods. 
• Soybean pod setting is nearing completion, and over half of Wisconsin’s corn crop has reached the dough stage. NASS reports that some producers in northern counties have started chopping corn due to the dry conditions. 

Outlook

• Rainfall chances are slightly higher in the northwest counties, with lesser chances in the south. 
• The outlook for the August-September transition indicates statewide leans toward above-normal temperatures and near-normal precipitation. 
• September temperatures are uncertain statewide with equal chances. Precipitation is leaning slightly towards below normal along the northern border. 
• Fall temperatures are leaning towards above normal for almost all of Wisconsin. Precipitation is uncertain statewide except for the far northeast (below normal lean). 

Agronomic, Fruit, and Vegetable Considerations

Field Conditions

• Crop conditions are highly reflective of moisture throughout the state. Pockets of drought-stressed crops are scattered throughout Wisconsin.  

Forage Management

• Third crop hay harvest is nearing completion in northern areas of the state as fourth crop is occurring in the southern area. Use the Alfalfa Cutting Tool to plan your final cut to manage for persistence.  
• Read about the impacts of drought on alfalfa if your crop is affected.  
• Scout for potato leafhopper in alfalfa fields. Watch for hopper burn.   
• Silage season is quickly approaching with some fields already chopped. As dry down events start collecting moisture data, you can view reports using the Corn Silage Dry Down Monitoring Tool.      
• If your silage crop has been impacted by drought, read these harvest considerations.  
• In areas that are impacted by drought, take caution with annual forages such as sorghum-sudangrass for concerns related to nitrate toxicity.  

Pest Management

• Scout fields to note what weed species are part of a late flush or have escaped herbicide application.  
• Scout sweet corn for corn earworm. Late season moth migrations have increased.  
• Scout for Japanese beetles. 
• Check for silk clipping caused by corn rootworm adults. In general, there is no need to spray adults unless major pollination problems occur.   
• If your area has been dry, check the undersides of soybean leaves for spider mites. This pest causes pockets of yellowing and browning of leaves starting on field edges and working inward.   
• Tar spot has been located in Wisconsin. Have a plan if your crop needs fungicide. Learn more about using Disease Forecasting Tools.  
• Southern rust has been located on Wisconsin corn. Learn about scouting for this disease.  
• Red crown rot was confirmed in WI last year. Know what to scout for in your soybean fields this year.  
• Fall armyworm trapping has begun.  Counts remain low.

Manure Applications

• Reminder of Wisconsin’s NR 151 Runoff Rules with the timing of manure spreading and current runoff levels. Check DATCP Runoff Risk Advisory Forecast. 

Small Grains

• As you harvest, remember the importance of combine cleaning.
• After small grain harvest is the perfect time to plant cover crops. Review species options.  
• If you are planting winter wheat this fall, consider revisiting Small Grains Recommendations and Row Width and Seeding Rates in WI.  

Fruit Considerations – General

• Fruit sunburn has been observed across many fruit crops in southern WI. Consider removing this fruit while out picking to prevent other pests attracted to the volatiles released from impacting fruit.
• Several grape varieties (Frontenac, Marquette) have hit veraison in the last week or so. This may translate to increased bird and disease pressure (sour/bunch rot).
• Sanitation: remove and destroy (chop/compost) fallen fruit ~weekly to prevent any internally developing larvae from reaching maturity, and to limit the spread of disease.
• Apple and grape growers can reference the NEWA weather station network to monitor for disease infection periods in their area. Check out your nearest weather station: NEWA Weather Station Network (Cornell).
• Wisconsin fruit growers can reference the Midwest Fruit Pest Management Guide for a list of registered products and recommended best practices. View the MFPMG Online.

Fruit Considerations – Disease

• Black rot and fruit rot symptoms continue to be reported in vineyards around WI. Review this 2022 article by Dr. Leslie Holland on Fruit and Cluster Rots for more information on black rot and summer rot management.
• Warm and rainy weather conditions are ideal for bitter rot in apple orchards; see the article on bitter rot management from the July 4 WI Fruit newsletter.
• Sooty blotch and flyspeck continues to be observed in Southern WI, pushed along by warm, humid conditions. Continue monitoring NEWA models.

Fruit Considerations – Insects

• Apple growers should continue monitoring degree-day (base 50℉) accumulation for Codling moth.
• Japanese beetle pressure has lessened in Southern WI, though emergence may continue through September. Review best monitoring and management practices here: Japanese beetle.
• Apple maggot pressure is variable across the state. Growers should continue to use red sphere traps to monitor populations.
• Grape and berry growers monitoring spotted wing drosophila should continue checking and refreshing traps weekly.
• Grape berry moth has been observed in southern WI. Continue monitoring traps and using NEWA models.
• Check out the WI DATCP Orchard Insect Pest Bulletin for more information on current insect trap captures across the state.
• Overview of grape insect/mite monitoring and management: Grape Insects and Mite Pests, 2024 Field Season (Cornell, 2024).

Vegetable Considerations – Disease

• Brassica black rot spreads most readily in warm and humid conditions. As we move into late summer, increased dewy mornings can increase the risk of spread. Symptoms start as yellow v-shaped lesions that spread in from the leaf edge. Avoid working in plants when wet, promptly remove symptomatic plants, and remove plant debris at the end of the season. More management options
• Cucurbit downy mildew has been confirmed on cucumber in southwest MI. There are currently no reports in WI. Cases have been relatively low overall this year, but be on the lookout for symptoms while scouting for other diseases. Symptoms start as angular, vein bound yellow to pale green spots on the upper leaf surface. As the disease progresses, the lesions turn brown and grow together leading to browning of entire leaves. Under humid conditions a dark purplish-grey fuzz may form on the underside of leaves. 
• Angular leaf spot can be confused with downy mildew as lesions are tan and vein bound. As the disease progresses, the lesions become white and papery and fall off the leaves causing irregularly shaped holes. Leaf wetness can lead to bacterial ooze, a milky substance, on the underside of leaves. If you need help with id, please send photos or samples to the Plant Disease Diagnostic Clinic.  
• Continue scouting for powdery mildew. Focus on the underside of leaves and leaves that are shaded. Look for the characteristic white talcum-like colonies. Management includes growing resistant varieties, fungicides, and biologically based products. Michigan State University conducted trials last season on recommendations for both fungicides and biologically based products. Results can be found here 
• Potato early blight was confirmed in Buffalo County. Continue scouting regularly and apply preventative fungicides. Preventative measures allow for the most successful management. Guidance on fungicide options can be found here.  
• Late blight was detected on potato in southwest MI during the past week. Continue scouting and applying preventative fungicides. Symptoms include large irregular leaf lesions that are not restricted by leaf veins, dark brown lesions on stems, and brown to red to purple discoloration of internal tuber tissue.
• Scout table beets for symptoms of Rhizomania including yellowing and wilting of leaves, patchy field decline and hairy roots. This disease was first confirmed in WI in 2025. Disease development is favored by wet soil conditions and moderate temperatures.  
• Tomato early blight was detected in Buffalo County. Symptoms first appear on lower leaves and stems as circular brown spots. As lesions expand, they develop the characteristic bulls-eye pattern of concentric rings. The best control measure is prevention. Once symptoms appear, it can be difficult to control. Removing infected plants can help slow the spread. Fungicides must be applied very early, either before disease occurs or at first symptoms, to be effective. More management options 
• Tomato septoria leaf spot is common fungal disease. Leaf lesions are circular, tan to grey spots with raised fungal structures known as pycnidia. Stem lesions appear similar but are often darker in color. Fruit lesions are not common except under high levels of disease pressure. Management options include pruning, removing infected plants, and applications of fungicides containing copper or chlorothalonil.

Vegetable Considerations – Insects

• Crucifer flea beetles can be a problem on recent transplants. Scouting is recommended every 1-2 days in newly planted fields. Feeding often leads to a shot-gun appearance with circular holes randomly dispersed across the leaf. Management options
• Squash bugs continue to be a problem. Nymphs are the most susceptible life stage for control so be sure to be scouting regularly to be able to target this stage. Eggs generally hatch within 5 to 10 days after being laid. In small plantings, control options include remove eggs with adhesive tape, burning egg masses with a small torch, and cutting out small sections of leaves that have eggs. For larger plantings, there are organic and conventional insecticide options. Be sure to get good canopy penetration for the best control.
• Corn earworm, also known as tomato fruit worm, risk is high across the state. Check the DATCP trap network for counts in your area. Larvae range in color from olive-brown to maroon to black with yellow heads. Id can be tricky as larvae can look similar. This article from Purdue can help with ID. Management options 
• Areas in northern WI are experiencing drought conditions that are favorable for two spotted spider mites (TSSM). TSSM feed on solanaceous crops and cucurbits. Symptoms include pale, blotchy spots that give leaves a mottled appearance and visible webbing with heavy infestations. Management options include overhead irrigation, although water early enough in the day to allow leaves to dry, avoiding over applications of nitrogen, and chemical controls.

Temperature Trends

Growing Degree Days (Base 50°F)

Crop Progress and Condition