Seasonal distribution of rainfall

It is doubtless true that the total annual precipitation is the
chief factor in determining the success of dry-farming. However, the
distribution of the rainfall throughout the year is also of great
importance, and should be known by the farmer. A small rainfall,
coming at the most desirable season, will have greater
crop-producing power than a very much larger rainfall poorly
distributed. Moreover, the methods of tillage to be employed where
most of the precipitation comes in winter must be considerably
different from those used where the bulk of the precipitation comes
in the summer. The successful dry-farmer must know the average
annual precipitation, and also the average seasonal distribution of
the rainfall, over the land which he intends to dry-farm before he
can safely choose his cultural methods.

With reference to the monthly distribution of the precipitation over
the dry-farm territory of the United States, Henry of the United
States Weather Bureau recognizes five distinct types; namely: (1)
Pacific, (2) Sub-Pacific, (3) Arizona, (4) the Northern Rocky
Mountain and Eastern Foothills, and (5) the Plains Type:--

_"The Pacific Type.--_This type is found in all of the territory
west of the Cascade and Sierra Nevada ranges, and also obtains in a
fringe of country to the eastward of the mountain summits. The
distinguishing characteristic of the Pacific type is a wet season,
extending from October to March, and a practically rainless summer,
except in northern California and parts of Oregon and Washington.
About half of the yearly precipitation comes in the months of