Central States

The vegetation in the Central States region is mostly hardwoods, and mixed pine and hardwoods, interspersed with agricultural lands. The topography is mostly flat to gently sloping. The principal exceptions are the Missouri and Arkansas Ozarks and the western portions of the Appalachians. Summer temperatures tend to be high in the southern portion of the region, but relative humidities are usually high also. The northern portion experiences brief periods of high temperatures and brief periods of moderate temperatures as mT air masses alternate with either mP or cP air masses. Winters can be extremely cold in the north.

Annual precipitation is moderate, generally 20 to 45 inches, with snow and rain in the winter, and showers and thunderstorms in the summer. Usually, there is sufficient rain with thunderstorm activity to minimize lightning fire occurrence. The maximum precipitation usually falls in early summer in the north, but there is a fair distribution throughout the year in the southern portion. There are occasional dry summers, but the green tree canopies and green lesser vegetation are usually sufficiently effective in the summer to keep fires from being aggressive.

As in the Great Lakes region, the principal fire season is in spring and fall when the hardwoods are not in leaf and the lesser vegetation is dead. In the southern portion of the region the spring season is somewhat earlier and the fall season somewhat later than in the northern portion.

The synoptic weather patterns producing high fire danger in the Central States are similar to those affecting the Great Lakes region, except that the Bermuda High type influences the southern portion of the Central States region more frequently. Nevertheless, the Bermuda High is the least important of the types, both from the standpoint of frequency and from the fact that it occurs mainly during the summer months when vegetation is green. The Pacific High, Hudson Bay High, and Northwestern Canadian High types, in that order, cause nearly all of the high fire danger in spring and fall. These types have been described above for adjoining fire climate regions.