Most farmers and agronomists I have visited with were grateful for the warm September experienced during 2004. Most feel that without it we would have had few crops develop to maturity. But, how good was September?

Data collected from the Arlington and Marshfield Agricultural Research Stations show that by May of the 2004 production year accumulated precipitation was above the 30-yr average (Figure 1). By the first part of September total precipitation was equal to the 30-yr average. No days at either location had maximum temperatures above 90 F, and rarely were daily maximum temperatures above the 30-yr average. Towards the end of August a scare occurred were the minimum temperature was 35 F on August 21. Growing degree units (GDUs) begin to lag behind the 30-yr average by early June. We needed a warm September to finish the crop.

Typical GDU accumulation during September averages 381 GDUs at Arlington and 330 GDUs at Marshfield . The coolest September on record at Arlington occurred in 1993 with 260 GDUs and at Marshfield in 1965 with 211 GDUs. The warmest September on record was 1971 at Arlington and 1931 at Marshfield (Table 1). During 2004 GDU accumulation was 419 GDUs (10% more) at Arlington and 446 GDUs (35% more) at Marshfield . At both locations a killing frost did not occur until early October.

Clearly September was one of the warmest on record at Marshfield and helped with the rate of crop development. We have seen warmer Septembers in other years at Arlington .

Table 1. Rank of years for Growing Degree Unit accumulation during September since 1962 for Arlington and since 1913 for Marshfield (modified GDUs base = 50 F, max = 86 F).
	Arlington		Marshfield
Rank	Year	GDUs	Year	GDUs
1	1971	483	1931	452
2	1978	472	2004	446
3	1998	470	1948	444
4	2002	459	1998	443
5	1988	456	1933	430
6	1994	443	1994	426
7	1990	442	1920	421
8	2004	419	1936	406
9	1979	414	1921	403
10	1996	408	1990	399