Crop & Pest Report


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Weather Forecast (07/23/20)

The July 23 to July 29, 2020 Weather Summary and Outlook

Western North Dakota has been closer to average or below average for the past few weeks, but eastern North Dakota into northwestern Minnesota has been mostly above average.  In fact, Fargo (KFAR Airport data) as an example, just ended a period of 26 straight days with a maximum of 80° or higher on July 20 when the high only reached 79°.  That was tied with 1936 for the 4th longest such period on record.  That is a testament to the persistent warmth some parts of the region has experienced this summer.  These past 7 days as expected were below average at most North Dakota Agricultural Weather Network (NDAWN) stations (Figure 1).  Starting today (Thursday, July 23, 2020) temperatures will be warmer than average with some 90s returning for a couple of days.  The overall period from July 23 to July 29 is expected to be near or above average at most NDAWN locations.


There were two main periods of rainfall this past week.  The combination of two thunderstorm complexes made for some significant rain amounts in eastern North Dakota into central and western Minnesota.  Total rain for the period of July 15 through July 21 can be found in Figure 2.


May and most of June was dominated by the upper-level wind blowing in from the northwest and in turn, with a few exceptions the area recorded minimal precipitation.  These past three weeks there has been a trough of low pressure over Montana into the Canadian Rocky Mountains.  This causes the upper-level wind to blow from the southwest, by far the wettest pattern for the Northern Plains.  This same pattern will continue through the weekend.  There appears to be two thunderstorm complexes that will impact, especially eastern North Dakota into Minnesota this weekend.  One Friday Night into Saturday morning and the other Saturday Night into Sunday morning.  Once the second wave passes through; the upper level wind will shift to the northwest once again as a ridge of high pressure builds over the Rocky Mountains.  The tools I use for long range forecasting suggests that ridge may become the dominate flow during the month of August, meaning, if true, our region would experience a drier flow.

In the short term, because we will continue to record additional rains, especially this weekend, plus, soils are saturated in many parts of the central and northern Red River Valley, the number of hours with relative humidity above 85% should be substantial once again during this forecasted period.  The estimated hours with high relative humidity is presented in Figure 3.


The projected growing degree days (GDDs) base 32°, 44° and 50° for the period of July 16 through July 22, 2020 can be found in Figure 4.  Most locations are expected to record between 10 and 20 percent more 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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