The precipitation probability table can be used in several different ways. For example, the chance of having a specified monthly precipitation amount for a given month can be easily determined. The table shows a precipitation value of 2.30 inches for the probability level 0.30 in August. Let's further assume, in our hypothetical example, that the station has a normal August precipitation 3.76 inches. Similarly, the Freeze Data table has many uses.
Analogous data is given for the last occurrence in the spring.
Frost-free periods are those for which the daily minimum shelter temperature exceeds the threshold value of 36 degrees F. Growing degree units are often used as an indicator of crop development, and for classifying regional agroclimates. Return to U.S. Normals home page.