26 MISC. PUBLICATION 303, U. S. DEPT. OF AGRICULTURE 
REGION 25, OZARK-OHIO-TENNESSEE RIVER VALLEYS 
Humid, mesothermal, with adequate precipitation at all seasons. 
In the extreme southwestern portion subhumid. Much alternate 
freezing and thawing in winter. 
Average annual number of days with snow cover, 10 to 30 in the 
north, 1 to 10 in the south. Average annual frost-free season 160 
days in the north to 200 in the southeast and 240 in the southwest. 
REGION 26, NORTHERN GREAT LAKES-ST. LAWRENCE 
Humid, microthermal, with adequate precipitation at all seasons. 
There are two local portions in northern and southern New York 
that are wet rather than humid. 
Average annual number of days with snow cover, 90 to 120 in the 
southern portions to more than 120 northward. Average annual 
growing season less than 100 days in the north and at higher eleva- 
tions to about 130 in the south. 
REGION 27, APPALACHIAN 
Northern portion humid, microthermal; southwestern and south- 
central portions humid, mesothermal. Local areas of wet micro- 
thermal climates are distributed along the backbone of the mountains, 
and there is a wet mesothermal area in the southeastern portion. 
Average annual number of days with snow cover 1 to 10 in the 
extreme southern portion to as much as 90 in the extreme north. In 
the central portion 30 to 60 days is commonest. Average annual 
frost-free season 130 days in the north, especially at higher eleva- 
tions, to 210 days in the extreme southern portion. Throughout, the 
season is shorter with increasing altitude. 
REGION 28, PIEDMONT 
Generally humid, mesothermal, but microthermal in the extreme 
northern portion, with adequate precipitation at all seasons. Warmer 
than region 27. 
Average annual number of days with snow cover 1 to 10, decreasing 
southward to less than 1, increasing northward from 10 to 30. Aver- 
age annual growing season from 170 days in the north to 220 or 
more in the south, longer coastward. 
REGION 29, UPPER COASTAL PLAIN 
Humid, mesothermal, rainfall adequate at all seasons, Average 
annual number of days with snow cover less than 1 in the southern 
half, 1 to 10 in the northern half. Growing season 200 days in the 
north to 260 days in the south, longer coastward. 
REGION 380, SWAMPY COASTAL PLAIN 
Humid, mesothermal, with adequate precipitation at all seasons 
except in the extreme west where it gradually diminishes to a de- 
ficiency at all seasons. In central Florida the climate is subhumid, 
rather than humid. 
