Sub-Pecific. This regime is characterized by a fairly even distribution 
of precipitation (including snow) throughout the autum, Winter, and 
spring months and by fairly dry summers. The maximm precipitation 
falls during the winter months. Above 2500 feet, which may be taken 
as the mean elevation of the lowlands, the yearly average precipita- 
tion varies from twenty to forty inches or more, increasing more or 
less directly with the elevation. Below 2500 feet, the average falls 
below twenty inches, especially in the extreme southwest corner and 
in the canyon of the Clearwater River. The heaviest precipitation 
(above forty inches) occurs within the mountains, a triangular region 
whose apex is approximately at Burke, and whose base lies on a line 
drawn from the Oxford Ranger Station to Fish Lake in the Clearwater 
Forest. 
The variation in amount of rainfall from year to year is 
noteworthy. For a thirty year period at Port Hill the total precipi- 
tetion for the driest year was 15.42 en for the wettest 38.63 
inches; at Murray for a 15 year period, 26.73 for the driest, 45.31 
for the wettest; at Moscow for a thirty year period, 10.98 inches for 
the driest, 30.17, for the wettest. The number of days with .01 inch 
or more of rain varies in the lowlands from eighty-five to ninety days, 
with 140 days or more in the mountains. 
A climatic factor which has an indirect but profound effect 
upon the vegetation is the occurrence during the dry season of elec- 
trical storms accompanied by little or no precipitation. These are 
an important ©" 8 of Yorest fires inasmuch as they commonly occur 
= TR ll owe 2 
