A series of weeks in which the southern and central tiers of Minnesota have seen slightly higher-than-average temperatures have narrowed the gap and brought many locations close to the average number of heat units for this time of year, according to the latest government crop reports.

A cool, wet spring meant crops got off to a slow start this year, but observers find that, as many locations post weekly averages about two degrees above normal for the week, they are catching up on the necessary heat to grow the crops. With weekly average temperatures in the low 70s, the average daily accumulation of heat units is approximately 20 growing degree days. Some typical examples are Willmar and Worthington.

Willmar, in the west central region, had a weekly average temperature of 74 degrees this past week-about 2.7 degrees above normal, and went from a deficit of 81 heat units down to 60 GDDs below average.

Worthington, in southwest Minnesota, went from being only six degrees behind the average for accumulation of heat units in the last week of July, to being 12 units ahead of average for the end of this week.

Agricultural scientists Gyles Randall and Thomas Hoverstad at the Southern Research and Outreach Center in Waseca, calculate that the crop at the south central research station is about four days behind on heat units. The latest NASS report estimates that, with a seasonal total of 1418 growing degree days, Waseca is 70 units behind normal.

Measuring corn crop progress, the USDA-NASS field office found that 82 percent of Minnesota's corn has reached silking stage, compared to 95 percent for a five year average. About a tenth of the crop has now reached the milk stage in kernel development, compared to 40 percent for the five-year average.