Climate Summary
Well, sometimes the forecast does not pan out the way you thought it would. This time last week, we anticipated a wet week (0.5-1.5 inches of rain) with drying conditions expected to begin over the weekend. Then came along the omega block – a somewhat rare set-up with high pressure in the central US and low pressure and stormy weather in the west and Ohio Valley. This persistent pattern has brought endless days of precipitation to the state. Precipitation over the last seven days has totaled 1-6 inches statewide, with the heaviest rainfall located along and southeast of about I-71 (Figure 1). After early week warmth, the omega blocking pattern brought chilly temperatures to Ohio over the weekend, with highs in the 40s and 50s. Despite the weekend chill, growing degree days jumped another 85 units, now ranging from about 282 units in Ashtabula to more than 525 units across southern Ohio. Daily average soil temperatures have cooled as well, raning from the low 50s across the north to the low 60s in southern counties. For the latest up-to-date conditions, seasonal outlooks, and monthly climate summaries, please visit the State Climate Office of Ohio.
Figure 1: Total precipitation (inches) over the last seven days, ending at 8 am EDT Monday May 5, 2025. Figure courtesty of the Ohio River Forecast Center in Wilmington, Ohio
Weather Forecast
he beginning of this week will be dominated by the omega block pattern, easing by mid to late week. Showers and few rumbles of thunder will continue to rotate around low pressure in the area through Wednesday morning. The heaviest rain during this period will fall across northwest Ohio. Temperatures will remain chilly with highs in the 50s and 60s through Thursday. Drying conditions will start to take hold on Wednesday, even though a shower cannot be ruled out across southern Ohio on Thursday. A warming trend with dry conditions should persist for Friday through Monday, with highs getting back into the 70s for the weekend. We could see some patchy frost Friday and Saturday mornings, but widespread freeze conditions are not anticipated at this time. Overall, the the National Weather Service is currently forecasting 0.1-0.25 inches of rain near the Ohio River, 0.25-0.5 inches in north central Ohio, and 0.5-1.5 for all other locations over the next seven days (Figure 2).
Figure 2). Precipitation forecast from the National Weather Service for 8pm May 5 - 12, 2025.
The 6-10 day outlook from the Climate Prediction Center and the 16-Day Rainfall Outlook from NOAA/NWS/Ohio River Forecast Center show stronger probabilities toward warmer than normal temperatures and below normal precipitation (Figure 3). Climate averages include a high-temperature range of 68-72°F, a low-temperature range of 48-52°F, and weekly total precipitation of 0.90-1.15 inches.
Figure 3) Climate Prediction Center 6-10 Day Outlook valid for May 11 – 15, 2025, for left) temperatures and right) precipitation. Colors represent the probability of below, normal, or above normal conditions.
New Experimental Weed Emergence Tool
Our partner, the Midwestern Regional Climate Center, supported by the USDA National Institute of Food and Agriculture Crop Protection and Pest Management Program through the North Central IPM Center, has developed the experimental Weed Emergence Scouting Tool (W.E.S.T.) to help farmers estimate when agronomic weeds are likely first to emerge and reach peak emergence based on growing degree day (GDD) models. The tool uses GDDs to determine expected peak emergence, currently for giant ragweed and waterhemp (Figure 4). For more information, please visit the site.
Figure 4) Experimental Weed Emergence Scouting Tool courtesy of the Midwetern Regional Climate Center. The map shows the current forecast as of May 3, 2025 for the first emergence of waterhemp across the Midwest. Users may hover over their county of choice to get a specific forecast, as shown at the bottom of the figure.