Carolina Cotton Notes

I have looked at the long-term forecast for Raleigh (http://www.weather.com/weather/tenday/27695?from=36hr_topnav_undeclared)
Heat units are calculated by adding the high and the low, dividing that number by 2 and then subtracting 60
[(*F Max + *F Min Temp)/2] - 60 = DD60s. You can update these numbers for you local conditions and for changes in the forecast that will likely become more accurate closer to the actual day of planting.

Table 1. Here is a look at how heat units (DD60’s) are predicted for the next 10 days.

Date	High Temp	Low Temp	Daily DD60's	Predicted DD60 accumulation for the following 5 days
May 5	73	56	4.5	38 (May 5 - May 9)
May 6	80	57	8.5	56 (May 6 - May 10)
May 7	85	63	14	57.5 (May 7 - May 11)
May 8	82	66	14	51.5 (May 8 - May 12)
May 9	83	57	10	47 (May 9 - May 13)
May 10	79	60	9.5	51.5 (May 10 - May 14)
May 11	79	61	10
May 12	80	56	8
May 13	79	60	9.5
May 14	83	66	14.5

You can see in Table 2 below that the predicted heat units for the coming week are pretty good for cotton.

Table 2. The relationship between DD60's and planting conditions.

DD60's accumulation in the 5 days following planting	Planting Conditions
Less than 10	Very Poor
11 to 15	Marginal
16 to 25	Adequate
26 to 50	Good
>50	Excellent