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Weather Products: Cotton Planting Forecast

Last updated April 23, 11:30 p.m. (Provided by 6:30 a.m. daily, March 3 - May 6, 2014)
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5-day Forecast of Fahrenheit Degree-Days
Date San Joaquin Valley Sacramento Valley
Fresno Bakersfield Chico
Degree-Days^ Temp
Min/Max*
Degree-Days^ Temp
Min/Max*
Degree-Days^ Temp
Min/Max**
April 24 7.9 53/81 6.9 51/80 3.5 49/73
April 25 3.1 56/69 5.2 55/74 0.0 48/60
April 26 1.3 48/67 0.7 48/65 0.6 43/65
April 27 3.6 47/74 2.9 47/72 1.8 47/69
April 28 9.1 54/83 8.3 53/82 5.6 49/78
TOTAL 25   24   12  
Planting Guidelines using 5-day Degree-Day Forecast
Forecast
Degree-Days
Planting
Conditions
> 20 Ideal
16 - 20 Adequate
11 - 15 Marginal
< = 10 Unfavorable

An evaluation of the accuracy of UC cotton planting forecasts for 1998 through 2002, for Bakersfield and Fresno showed:

  • In March, planting only on days with ideal category forecasts (which occurred on 25% of March days), can likely avoid the need to replant due to incorrect forecasts predicting favorable planting conditions.
  • In April, following the forecast is quite safe, since it failed to predict unfavorable planting conditions (which occurred on 29% of April days) on average only 1 day out of 30 April days.

See the article for details.

The 5-day forecast of degree-days (heat units) is provided to help California's San Joaquin Valley and Sacramento Valley cotton growers determine suitable weather to plant cotton and avoid chilling injury to emerging cotton seedlings. This forecast, with the planting guidelines, should be used in conjunction with soil temperatures (at seed depth) above 58°F for timely, vigorous seedling establishment.

The degree-day forecasts are based on the best available weather forecast from National Weather Service. However, local conditions may cause some variation. Use your judgment if your local temperatures are different. If your min/max temperatures are above those reported, then your degree-days will be higher; if your min/max temperatures are below those reported, then your degree-days will be less.

The degree-day accumulations are calculated using the single-triangle method and a lower threshold of 60°F with no upper threshold. Forecast temperatures were accessed from the National Weather Service Web sites for Hanford and Sacramento.

^ Calculated by UC IPM using the single-triangle method, a lower threshold of 60°F with no upper threshold.

* Forecast temperatures accessed from the National Weather Service San Joaquin Valley Web site.

** Forecast temperatures accessed from the National Weather Service Sacramento Valley Web site.


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