May 21st, 2026 Weather Outlook

Key Points

Recent Conditions

• Temperatures were 2-5°F above normal across the western and southern counties. Further east, temperatures were close to normal. 
• Precipitation totals were highest in a belt stretching from the southwest to east-central counties last week (150% of normal or greater). Outside of this region, precipitation totals were typically near to below normal. 

Impact

•   Soil moisture levels at the 4” depth across UW research farm stations (Wisconet) were a mixed bag but showed an increase at locations that received an inch or more of rain.  
• Satellite-based soil moisture models indicate gains in soil moisture in a SW-to-NE belt, with abnormal dryness still indicated across the north and southeast. 
• Corn and soybean planting continue to make large strides, thanks to another week with over 6 days that were suitable for fieldwork. 
• Wisconsin remains drought-free with no changes in drought coverage or severity in the state compared to last week.   

Outlook

• Rain chances over the next 7 days are highest in southern and eastern counties. 
• Temperatures for the May-June transition are showing a likelihood (60-70% chance) to be above normal, with a lean towards near normal precipitation for most. 
• Across most of Wisconsin, temperatures and precipitation for June and summer (Jun-Aug) are uncertain currently with equal chances for above, near, or below normal conditions. 

Agronomic, Fruit and Vegetable Considerations

Field Conditions

• Avoid trafficking fields in wet conditions to prevent compaction and rutting.  
• While much of the state is out of the risk for frost conditions, check emerging crops in the wake of cool temperatures. Corn’s growing point remains underground through the V5 stage; however, exposed leaf tissue can be damaged, slowing early development and reducing uniformity. Soybean plants at the cotyledon stage are more resilient to cold temperatures. Conduct stand counts to determine population. See the corn and soybean replant guides.   

Forage Management

• First crop alfalfa is being harvested in select fields in Southern WI. Consider using a PEAQ (Predictive Equations for Alfalfa Quality) stick to estimate relative feed value as you decide when to make the first cut. 
• As scissor clips begin throughout the state, find UW and UMN quality data using the Alfalfa Harvest Alert dashboard.   

Pest Management

• Start scouting fields on foot to note which early weed species are emerging.  
• Be observant of black cutworm and true armyworm moths migrating through the state. Check the DATCP Pest Trap Network Maps.  It is likely that first generation true armyworm will miss corn crops. The second generation is of most concern. Watch the 2026 True Armyworm Forecast. 
• Primary seedling corn damage for black cutworm is in the second half of May. Scout emerging corn for signs of cutworm feeding.  
• Ensure temperatures are conducive to herbicide applications. Pre-emergent herbicides require moisture for activation.  
• Monitor insect degree days. Start scouting for alfalfa weevil at 300 DD. Weevil larvae have the greatest impact (quality and yield) on first and second alfalfa cuts. Be sure to walk fields looking for evidence of this pest. Larvae are appearing in Southern WI.  
• SlugNet is trapping again in 2026! Review weekly trap catches across the state. Observe fields (especially fields with reduced tillage and cover crops) for any signs of slug damage.  

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

• Scout small grains for signs of disease. This includes powdery mildew and stripe rust, especially in susceptible varieties. Use the Crop Risk Tool and Fusarium Risk Tool for guidance as Fusarium Head Blight becomes the next disease of concern. 
• Avoid fertilizer applications in wet and cool conditions. Nitrogen loss is greater in wet conditions. Review small grain fertility. Feekes 5 is the stage where fertilizer and herbicide applications should take place. Review growth stages here.  

Fruit Considerations

• 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. 
• Apple growers can reference the NEWA weather station network to monitor disease infection events for apple scab and fire blight. Make sure to keep track of green tip and petal fall dates. Check out your nearest weather station: NEWA Weather Station Network (Cornell). 
• Fruit growers impacted by spring freeze damage may reference our recent article on Resources for Fruit Growers Impacted by Spring Freeze Events. 
• Codling moth have been captured in Southern WI. Make sure to check traps after warm, calm evenings to establish a biofix date. Biofix occurs when ~5 or more moths are captured in one evening, or captured across consecutive nights. First generation larvae will emerge after ~250 degree-days base 50℉ from the biofix date. 
• Keep track of degree-days (base 50℉) from petal fall to determine the end of plum curculio movement into the orchard. Plum curculio will continue movement into the orchard until ~308 degree-days base 50℉ have accumulated from petal fall. 
• Grape growers can begin fertilization prior to bloom and should review last year’s petiole analysis to determine nutrient needs. Check out this recent UW Fruit News article on Fertilizing Wine Grapes. 
• Grape growers may reference our recent article on Post-Freeze Disease Management. 
• Apple growers may reference our recent article on Thinning After a Frost Event. 

Vegetable Considerations

• 4-inch and 8-inch soil temps are in the 60s in the early morning in some parts of southern WI. The rest of the state remains in the 50s with the exception of a few sites in northwest WI that are still in the high 40s. For pumpkin and squash wait until soil temps are at least 60°F and danger of frost has passed. For melons, soil temperatures are ideally 70°F, but if you want to plant early, check to make sure soil temperatures do not get below 60°F during the early morning and that air temperature is not forecasted to drop below 50°F. For crops like tomatoes and peppers in the field, wait until soil temps are at least 60°F but ideally 65-70°F.  
• Ensure garlic is receiving adequate moisture, between 1 and 2 inches per week, during bulb formation. For more information on growing garlic, check out this resource from Michigan State.  
• Start scouting for Colorado potato beetle as potato plants emerge. Focus on border rows and scan soil surrounding plants to help with early detection as adults will drop from plants as a defense tactic. The highest density is typically in fields adjacent to last year’s crop. Adults will begin laying eggs 7-10 days after initial colonization. Examine the underside of leaves to look for bright yellow to orange eggs that are laid in clusters. Initial perimeter applications may begin in the next week. Check out the latest Vegetable Crop Update for more information.  
• Striped cucumber beetles over winter in WI and emerge in mid to late May. Eggs are laid at the base of cucurbit plants. Once larvae hatch, they feed on roots and stems and can cause stunted growth or even kill seedlings. Adults feed on foliage and fruit and can spread bacterial wilt which can cause severe losses in cucumber and muskmelon. It is important to scout and, when necessary, control beetles early in the season to reduce risk of spreading this bacterial wilt. Control measures include dipping seedlings in kaolin clay prior to transplanting, floating row cover or high tunnel insect exclusion screens, and perimeter trap cropping. 
• The risk of western flower thrips is now high or very high in southern and into central WI. Early detection is key as control can be very difficult. Iowa State has a few useful videos on scouting: tip on finding thrips and tips on spotting thrips damage on cucumber transplants. One option to reduce risk is dipping plants in a horticultural oil or insecticidal soap right before transplanting. Some other control options include row cover, reflective mulch and weed management as weeds such as chickweed and lambsquarters serve as alternative hosts.  
• Damping off of seedlings is caused by Rhizoctonia, Fusarium and Pythium. These pathogens are soil borne and thrive in cool and wet conditions. Seedlings are susceptible for a short time following emergence, but susceptibility declines quickly as the plants grow. Infection leads to lower stem girdling and collapse. Some treatment options include planting as shallowly as agronomically allowable to encourage quick germination, not overwatering, and using fungicides treated seed.  
• Risk of crop damage from asparagus beetle larvae is now high or very high for most of northern WI with the exception of counties close to Lake Superior. Risk will be decreasing in central WI over the next week as peak larvae activity has passed. When scouting, sample twenty plants from five different areas to determine if you have reached the threshold for treatment. Row cover can be a good option to exclude the beetles if eggs have not already been laid. 
• Imported cabbageworm adults, white butterflies with black markings on wingtips, are now active throughout the state with the exception of along Lake Superior. Start scouting for eggs which are laid as a single egg that are yellow to orange in color. Young plants can be particularly susceptible to damage so either use insect netting to exclude adults if they are not yet active in your area or time insecticide spray to larval hatch. 
• Start scouting for diamondback moths which overwinter in WI as adults. Adults fly at night so can be hard to detect. When scouting, look for eggs on the underside of leaves. Eggs are flat and cream colored and can either be laid singly or in a cluster. They will hatch within about a week of being laid. Floating row covers work well to protect small plantings and a parasitic wasp, Diadegma insulare, can do a good job of keeping this pest in check. Young transplants are more susceptible to damage so the threshold for management is when 10% of plants are affected.  
• Swede midge is another brassica pest. They feed on growing points leading to distortion and scarring on leaves. Depending on when infestation occurs, they can also lead to uneven or even complete loss of a head or crown. While there are pheromone traps for swede midge, they can be difficult to use as it is hard to distinguish from other flies. They can be difficult to detect because larvae hide in growth points but an indicator can be a wet growing tip due to burst cells from larvae feeding. Some control options include insect netting, avoiding the use of brassica cover crops, and removing brassica weeds that can serve as alternative hosts.  
• Onion maggot adult flight peaks are occurring now in NW WI around Rice Lake, central WI around Wausau and Appleton, and SE counties along Lake Michigan. Use the Vegetable Disease and Insect Forecasting Network to see the risk in your area. Preventative soil insecticide applications are recommended for the first generation larvae if damage to the last year’s crop was over 5-10%. For small plantings of onions, row cover can be effective if adults are not yet active in your area. 
• Risk from the first generation of adult seed corn maggots is now very high in northern WI and the second generation is starting to move into southern WI.  If possible, delay planting crops including beets, green beans, and pumpkins until the risk has decreased. If you cannot delay planting, promote faster germination by planting seeds as shallowly as agronomically possible. More management options can be found here.  
• Cabbage maggot peak egg laying is now occurring in southern and central WI. Cabbage maggots overwinter as larvae in the top several inches of soil. When the adults emerge, they are attracted to freshly tilled fields with decaying organic matter. They thrive in wet and cool conditions. Treatment is primarily preventative. When possible, till in cover crops 2 to 3 weeks before planting to reduce attractiveness. If possible, delay planting to avoid peak emergence. Floating row covers are also a good option during peak activity. To monitor activity in your area, use the Vegetable Disease and Insect Forecasting Network.  
• Black cutworm moths are starting to migrate into WI with trap catches reported by DATCP. Check the DATCP trap catch maps for counts in your area. Black cutworm larvae feed on newly emerged crops and prefer direct seeded crops over transplants. Many crops are susceptible to damage including beets, carrots, cucumber, leafy greens, sweet corn and squash. Management options include weed management as females prefer to lay eggs in weedy areas and avoiding the use of green manure in areas where cutworms tend to be a problem. For chemical control to be effective, early detection is key. If chemical treatment is necessary, begin treating at the first signs of cutting and repeat every 7 days until 1000 degree days are reached.  

Temperature Trends

7 Day Temperatures

Image Description ↓

A map titled “Average Temperature (°F)” with subtitle “May 12, 2026 to May 18, 2026” shows Wisconsin and surrounding Upper Midwest regions. A color scale at the bottom ranges from 45°F (darker green) to 70°F (yellow), with intermediate greens and light yellow tones. Most of Wisconsin is shaded green, indicating average temperatures around 50–60°F. Northern Wisconsin shows darker green shades (about 45–55°F), especially near Lake Superior. Central and eastern areas, including Green Bay and Milwaukee, are light green (roughly 52–58°F). Southern Wisconsin, including Madison and areas southwest, transitions to light yellow-green, indicating warmer averages around 58–65°F.

Image Description ↓

A map titled “Average Temperature (°F): Departure from 1991–2020 Normals” with dates “May 12, 2026 to May 18, 2026.” The map shows Wisconsin and surrounding Upper Midwest regions. A color scale at the bottom ranges from -6°F (dark green, below normal) to +8°F (dark brown/orange, above normal). Most of Wisconsin is shaded light to dark orange, indicating above-normal temperatures. Western and southwestern Wisconsin, including areas near Eau Claire and Madison, show the largest positive departures (about +4 to +7°F). Central Wisconsin shows moderate positive departures (approximately +2 to +5°F). Northern and northeastern Wisconsin include lighter colors and small patches of green, indicating near-normal to slightly below-normal conditions (around -1 to +2°F), especially closer to Lake Superior and parts of the Lake Michigan shoreline.

• Average temperatures ranged from 60-65°F in the south and west to 50-55°F in the far north and northeast. 
• Temperatures were 2-5°F above normal across the western and southern counties. Further east, temperatures were close to normal. 

30 Day Temperatures

Image Description ↓

A map titled “Average Temperature (°F)” with dates “April 19, 2026 to May 18, 2026” shows Wisconsin and surrounding Upper Midwest regions. A color scale at the bottom ranges from 40°F (dark green) to 60°F (light green). Most of Wisconsin is shaded medium green, indicating average temperatures around 45–55°F. Northern Wisconsin, especially near Lake Superior, shows darker green tones (about 40–48°F), representing the coolest conditions. Central Wisconsin trends slightly warmer in mid-green shades (around 48–52°F). Southern and southeastern Wisconsin, including Madison and Milwaukee, are lighter green, indicating warmer averages near 50–55°F.

Image Description ↓

A map titled “Average Temperature (°F): Departure from 1991–2020 Normals” with dates “April 19, 2026 to May 18, 2026” shows Wisconsin and surrounding Upper Midwest regions. A color scale at the bottom ranges from −5°F (dark green, below normal) to +3°F (tan/orange, above normal), with gray indicating near-normal conditions. Most of Wisconsin is shaded light to medium green, indicating below-normal temperatures of approximately −1 to −3°F, especially across northern and central regions. Northeastern Wisconsin near Green Bay shows areas closer to near normal (−1 to 0°F). Southern Wisconsin, including near Madison and southwestern counties, includes patches of tan/orange indicating slightly above-normal temperatures (about 0 to +2°F). Much of central and central-southern Wisconsin appears gray, indicating near-normal conditions.

Crop Progress and Condition

Crop Progress Report for Wisconsin for the Week Ending on May 18th

Image Description ↓

A U.S. map titled “Corn Progress – Percent Planted” with date “May 17, 2026,” from USDA. Each state shows a top number (percent planted) and a bracketed number (change from 5-year average). A legend shows color categories for change from “40% or more” (dark green) to “40% or less” (dark red).

Midwest and Plains states display values such as: North Dakota 58 [+18], South Dakota 81 [+16], Minnesota 86 [+12], Iowa 91–? (depicted ~high 80s [+6]), Nebraska 82 [+3], Kansas 63 [-5], Missouri 84 [+2], Illinois 75 [+2], Indiana 67 [+10], Ohio 52 [+12], Michigan 47 [-5]. Kentucky shows 90 [+20], Tennessee 96 [+11], and North Carolina 94 [-1]. Pennsylvania shows 43 [+1], and Texas 88 [+2]. Western states are mostly gray (no data shown).

A box labeled “National Progress” reads: Planted 76; Change from 5-year Average +6. A note explains: “Top ## – Percent Planted; [Bottom ##] – Change from 5-year Average.”

Image Description ↓

A U.S. map titled “Soybeans Progress – Percent Planted” with date “May 17, 2026,” from USDA. Each state shows a top number (percent planted) and a bracketed number indicating change from the 5-year average. A legend on the right classifies changes from “40% or more” (dark green) to “40% or less” (dark red).

Midwest and Plains values include: North Dakota 41 [+13], South Dakota 59 [+13], Minnesota 74 [+21], Iowa 80 [+12], Wisconsin 54 [+4], Illinois 74 [+11], Indiana 67 [+17], Ohio 46 [+11], Michigan 37 [-9], Nebraska 81 [+16], Kansas 53 [+9], Missouri 59 [+14].

Southern states show higher planting progress: Arkansas 90 [+12], Louisiana 94 [+17], Tennessee 80 [+32], Kentucky 76 [+31], North Carolina 61 [+16]. Most displayed states are ahead of the 5-year average (green shades), with Michigan and a few areas slightly below (yellow/orange).

A box labeled “National Progress” reads: Planted 67; Change from 5-year Average +14. A note explains: “Top ## – Percent Planted; [Bottom ##] – Change from 5-year Average.”

• Wisconsin had 6.1 days suitable for fieldwork statewide, thanks to a dry week for most. 
• Corn planting is at 62% complete, up from 31% last week. Corn is 13% emerged. 
• Soybean planting is at 54% complete, up from 26% last week. Soybeans are 9% emerged. 
• Oat planting is 68% complete, compared to the average of 75%. Emergence is at 36% complete.  
• Pasture and range were rated 57% good to excellent, up 3 percentage points from last week. 
• Winter wheat was rated 62% good to excellent, up 3% from last week. Winter wheat is 4% headed. 
• The first cutting of alfalfa is just getting underway.  
• Read the full USDA report. 

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