Crop & Pest Report


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Weather Forecast (07/30/20)

The July 30 to August 5, 2020 Weather Summary and Outlook

It has been very common this growing season for eastern North Dakota and northwestern North Dakota to be above average for temperatures and western North Dakota to be near or slightly below average. That was the case this past week as well (Figure 1).  The temperatures the next seven days are expected to be near or below average across the entire area. A bit of a departure from what the region has recorded since mid-May.


There was one main period of thunderstorms this past week that occurred last Friday into Saturday (July 24 and 25). The thunderstorms dropped significant rain across south central and eastern North Dakota. Total rain for the period of July 23 through July 28 can be found in Figure 2. Since that event it has been mostly dry and the upcoming week is expected to continue that trend. Like last week, there will be some areas that recorded little if any precipitation, especially in western North Dakota, whereas, most of eastern North Dakota into western Minnesota should record at least some moisture from some scattered thunderstorms expected Friday into Friday night.


As mentioned last week in my Crop and Pest Weather report, the upper level wind flow, at least for now, has switched back to the pattern we were in from the middle of May through most of June. That pattern of a ridge of high pressure aloft to our west and a trough of low pressure over the Great Lakes should continue through the first week of August. Overall, that will mean near to slightly above average temperatures and near to below average precipitation.  Yet, as previously mentioned, at least in the short term the temperatures will on most days be below average through the middle of next week.

The estimated hours with high relative humidity is presented in Figure 3. Because of the high soil moisture content in many parts of eastern North Dakota and northwestern Minnesota, in combination to some cooler nights foreseen in the next week, a high number of hours with relative humidity values above 85% are projected in the next seven days. This will mean a higher than average disease risk during this forecasted period.


The projected growing degree days (GDDs) base 50°, 44° and 32° for the period of July 30 through August 5, 2020 can be found in Figure 4. Most locations are expected to record around 10% fewer GDDs this period than during the past week.


Using May 1 as a planting date, accumulated growing degree days for wheat (base temperature 32°) is given in Figure 5.  You can calculate wheat growing degree days based on your exact planting date(s) here:


Using May 20 as a planting date, accumulated growing degree days for corn (base temperature 50°) is given in Figure 6.  You can calculate corn growing degree days based on your exact planting date(s) here:


Soybeans also use base 50° like corn, but NDAWN has a special tool for soybeans that based on your planting date and cultivar can estimate maturity dates based on average temperatures, as well as give you GDDs based on your planting date(s) you set. That tool can be found here:


Daryl Ritchison


Director of the North Dakota Agricultural Weather Network



This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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