Select climate stations that observe both temperature and precipitation. Precipitation only stations can be used if a neighboring station has the temperature information necessary to determine growing season. It should be noted that growing season dates are more important in the spring and fall and that wetlands determinations made in the middle of the growing season are more dependent on precipitation.
Select stations with a minimum of 20 years of data.
There may be a great variation in climate for an individual county, especially in the West. Therefore, it may necessary to review several climate stations and select one that represents the climate in the area under consideration.
Some areas of the country seldom experience temperatures of 28 degrees or less. These areas include coastal South Carolina, coastal Georgia, Florida, southern Alabama, southern Mississippi, southern Louisiana, coastal Texas, southern and coastal California, coastal Oregon, coastal Washington, the Pacific and Caribbean Islands. Thresholds temperatures of 34, 32, 28 degrees should be selected for these areas.