Temperatures over the Memorial Day weekend warmed to near average highs creating a very
nice weekend for campers and other enjoying outdoor activities. These near-average
temperatures were very uncommon for South Dakota this May. Much of the month has been
below average for temperatures for much of the state.

Cooler temperatures and moist soils in many areas slowed field work and limited the
development of seed already planted. Several county extension educators had reported a
slowed accumulation of GDDs. Let’s look at how GDDs (50-86) are accumulating compared to
average at a few example sites. (Note the slight difference in accumulation period)

The loss of GDDs early in the season comes at a time that could benefit crops since above
average temperatures would spur development usually without stressing the crop. Higher than
average temperatures would not stress the crop at this time of year, particularly where soil
conditions are moist. The seasonal accumulation will have to be monitored for continued slow
development.

Users can calculate their own GDD accumulation from data from the research farms around
the state at http://climate.sdstate.edu/w_info/Query/gdd.htm
Other stations will be added to this feature to provide more complete state coverage.

Dennis Todey
State Climatologist