Many of our pest problems in turf can be at least partially predicted through growing degree day models ( Poa annua seedheads is one example). Most of the models use a base temperature of 50 (abbreviated as GDD 50 ) assuming 50 degrees is the temperature when most of our biological activity starts occurring. GDD50 for IN can be downloaded from http://shadow.agry.purdue.edu/sc.obs-geog.html . The data are available as daily accumulations so download the data from the beginning of the year and add up the accumulated GDD. The data can be easily transferred to Excel or other spreadsheets to simplify the calculations. Dr. Karl Danneberger from Ohio State has two very nice articles on growing degree days on his SK Turf Notes web site at http://buckeyeturf.osu.edu/component/option,com_turfnotes/Itemid,84/noteid,741
http://buckeyeturf.osu.edu/component/option,com_turfnotes/Itemid,84/noteid,1017