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Weather Forecast (07/19/18)

The July 19 through July 25, 2018 Weather Summary and Outlook

This past week was another period of above average temperatures being recorded at most of the North Dakota Agricultural Weather Network (NDAWN) stations (Figure 1).  The upcoming seven day period may be the first week in quite some time to have widespread below average temperatures.


There were only scattered thunderstorms in the region this past week with most of the NDAWN stations not recording much precipitation (Figure 2).  There were locations that recorded over one inch of rain, but those heavier pockets of precipitation missed all of the NDAWN stations.


The persistent above average temperatures that have been recorded since the beginning of May looks to be ending as a pattern change is occurring in the Northern Hemisphere.  This trend toward cooler temperatures looks to be lasting beyond just the next seven days.  In fact, I would not be surprised if the second half of summer finishes with below average temperatures.  That doesn’t mean that there will not be periods of warmer temperatures, just as there has been pockets of cool intermixed with the warmth of the past two months.  Instead, it appears we will be experiencing more below average temperature days than above average temperature days for the next few weeks.  The projected growing degree days (GDDs) Base 50°, 44° and 32° for the period of July 19 through July 25 is presented in Figure 3.


This trend toward cooler air in combination with some rain in the area today (Thursday), Friday and late Sunday into Monday should lead to a high number of hours with relative humidity above 85% during the next week (Figure 4).  Below average temperatures this time of year tends to produce stronger air temperature inversions that lead to a higher risk of prolonged dew residing on plants for a longer period of time after sunrise.  That means hours with relative humidity plus the dew risk after sunrise may mean a potential for a higher number of hours with disease risk on plants than is projected by relative humidity, alone.


Using May 5 as a planting date, the accumulated wheat growing degree days (Based 32°) through July 17, 2018 is presented in Figure 5.  You can find your exact GDDs for your planting date(s) at this site.


Using May 10 as a planting date, the corn accumulated growing degree days (Base 50°) through July 17, 2018 is presented in Figure 6.  You can find your exact GDDs for your planting date(s) at:



Daryl Ritchison


Interim 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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