Comparing 2016 Summer Temperatures with 2015

Comparing 2016 Summer Temperatures with 2015 August 9, 2016

My office has been receiving a fair number of inquiries as to what impacts this growing season's weather trends have had on crops and whether bumper yields are likely to occur given USDA forecasts of baseline or better national corn yields. National yield forecasts the past 30 days have generally been in the range of 168 to 173 bushels per acre.

The purpose of this article is not to affirm these preliminary projections, but to more closely examine June-July temperature trends and how they compare to last year. "No two growing seasons are alike" goes the old adage and these seasons confirm that.

The stark difference between 2015 and 2016 was greatest in June (Table 1). Average temperatures in June were considerably higher this year than last: ranging from 1.4 degrees (Fahrenheit) in McCook to 5.3 degrees in Omaha and 5.4 degrees in Lincoln. The number of days reaching or exceeding 90°F was double to triple the number in 2015, depending on location in the state (Table 2).

The major contributing factor was the position of the jet stream with a mean trough over the western U.S. and an upper ridge over the eastern U.S. This allowed much warmer air laden with moisture from the Gulf of Mexico to dominate the eastern half of the state. Every location east of Grand Island experienced multiple days when low temperatures remained above 70°F, with Omaha recording 13 days. However, in June 2015, of the stations listed, only Lincoln recorded one day with minimum temperatures of 70°F or above (Table 3).

The temperature pattern in July 2016 was much more variable, as were the differences between that month and July 2015. Eastern Nebraska generally experienced fewer days when the maximum temperature reached 90°F in 2016 than in 2015; western Nebraska maximum temperatures were similar to or slightly warmer than those in July 2015. Minimum temperatures for July ranged from 2 degrees above to 2 degrees below July 2015 trends.

If we look at the temperature trend over the two-month period, eastern Nebraska locations averaged 2-3 degrees above 2015 trends for June-July, while western Nebraska locations were 1-2 degrees above 2015, with isolated pockets pushing 3 degrees (Table 1). When final grain yields become available for analysis this fall, it will be interesting to see whether the unusual number of maximum temperature days at or above 90°F or minimum temperatures at or above 70°F may have been a significant factor in production output.

During the two-month period (June- July) a total of 36 days reached 90°F in Omaha and Scottsbluff, while Norfolk had 16 days. A year ago, Omaha recorded 19 days, Scottsbluff 21 days, and Norfolk, 10 days. (It should be noted that temperatures the first seven days of June never reached the 90°F mark.)

Minimum temperatures were well ahead of 2015 levels this year with Omaha and Lincoln recording 18 and 27 days, respectively, when minimum temperatures never dropped below 70°F.  In short, the number of days when the minimum temperature failed to drop below 70°F was nearly double the number in 2015. For the remainder of the state, differences were not as dramatic, ranging from one to six more days in 2016.

Table 1. Average temperatures for June and July 2015 and 2016.
June
2015
June
2016
DiffJuly
2015
July
2016
Diff
Lincoln 73.4 78.8 5.4 77.1 77.8 0.7
Omaha 73.4 78.7 5.3 77.0 77.8 0.8
Norfolk 70.9 73.8 2.9 74.4 74.1 -0.3
Grand Island 74.5 76.4 1.9 75.6 76.0 0.4
North Platte 70.6 72.6 2.0 74.2 74.4 0.2
Valentine 69.0 72.4 3.4 73.4 74.1 0.7
Scottsbluff 70.8 73.6 2.8 72.5 75.8 3.3
McCook 73.6 75.0 1.4 77.4 78.0 0.6

 

Table 2. Days with a maximum temperature of 90°F or more in June and July 2015 and 2016.
June
2015
June
2016
DiffJuly
2015
July
2016
Diff
Lincoln 7 19 12 16 13 -3
Omaha 4 18 14 15 10 -5
Norfolk 1 9 8 9 7 -2
Grand Island 5 14 9 10 11 1
North Platte 5 12 7 11 11 0
Valentine 2 10 8 13 12 -1
Scottsbluff 6 15 9 15 21 6
McCook 9 12 3 18 18 0

 

Table 3. Days with a minimum temperature of 70°F or more in June and July 2015 and 2016.
June
2015
June
2016
DiffJuly
2015
July
2016
Diff
Lincoln 1 9 8 11 9 -2
Omaha 0 13 13 12 14 2
Norfolk 0 4 4 4 6 2
Grand Island 0 4 4 6 8 2
North Platte 0 0 0 1 1 0
Valentine 0 1 1 0 1 -1
Scottsbluff 0 0 0 0 0 0
McCook 0 0 0 3 4 1
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