Weather can often dictate every aspect of crop production from when the crops are planted all the way through harvest. Forecasted weather conditions may force growers to make or delay certain operations. High wind speeds might make pesticide applications too risky. Hail storms could damage crops. Threat of freezing temperatures might require the use of frost damage prevention techniques such as ventilation fans.

Even information about past weather conditions can be useful to growers. Soil temperatures and chilling hours can have a strong effect on crop germination and yields. Rainfall totals indicate how much supplemental irrigation is needed. A record of day temperatures helps growers time their pest control sprays so as to reach pests during certain parts of their life cycles.

Unless you have your own weather station, accurate and local information can be hard to find. Fortunately, the National Weather Service (NWS) and other organizations operate weather stations that are accessible online. Contra Costa County has about 30 Remote Automated Weather Stations (RAWS) whose information is available from the National Weather Service website. The three stations that are nearest the major farming areas in east county are: in Brentwood west of the Hwy 4 Bypass, along Bethel Island Rd. east of Oakley, and south of Los Vaqueros Reservoir southwest of Byron. For growers near the county lines, there are also online automated stations in the Altamont Pass, Tracy, and Stockton. To get data from the local automated weather stations, go to the San Francisco Bay Area/Monterey National Weather Service website at www.wrh.noaa.gov/mtr/. To reach the RAWS information, click on ?Observations? which will take you to the ?Current Weather? page.

When you click on the ?Interactive Map: East Bay?,it will bring up a map of all the RAWS in the East Bay. If you move your mouse indicator over a station, the most current information will be displayed. If you click on the station, it will take you to a page with data from the last two days. This is a detailed list of the values the station has measured over time increments that may be as short as every ten to twenty minutes. If a station has been taken out of service for maintenance, its indicator mark on the map will be missing. The type of information each station lists will depend on what agency operates it. For instance, stations operated by the Federal Aviation Administration at airports will include data such as visibility and cloud cover while Forest Service stations will list fuel moisture levels. Almost all of the stations list temperature, wind speed, and wind direction. Other useful information to growers that is often listed for many stations is wind gust speed and 24 hour precipitation.

Detailed local weather forecasts can also be found using the National Weather Service website. These forecasts are especially useful for planning pesticide applications. Growers may be required by law to be aware of and mitigate forecasted weather conditions. For example, dormant insecticide applications are prohibited when the National Weather Service has forecasted that a storm likely to cause runoff from the treated field is to occur within 48 hours.

To access detailed forecast information, start at the National Weather Service SF/Monterey website. Go down about half way down the page and click on the ?Forecast Weather Tables? icon (shown by the green arrow on the top right figure). You will then be taken to the Experimental Forecast Weather Table Interface (shown in the middle right figure). Once there, you can choose what area you want a forecast for either by entering the city and state in the location search box and clicking on the ?Go? button or by clicking on the map displayed in the lower part of the screen. Either will bring you to a table of the forecast information. If you want to redefine the desired forecast area, click on the map in the lower part of the screen.

The table will give forecast information in six hour time blocks during the next seven days. It is possible to set it to list shorter time intervals and a fewer number of days. (The wind speed forecasts are not available on the shorter time interval tables.) Information on the table includes the probability and expected amount of rain, temperature, cloudiness, dewpoint, humidity, wind speed, and wind direction.