The springs, as has been stated, are generally small and very numerous, and many of them are unfailing, though liable to be affected by drought. In such cases, by absorption and evaporation, the small streams are frequently exhausted before uniting and often render the larger ones too light for manufacturing purposes. Nevertheless, water power is abundant; the county's diversified elevation giving considerable fall to its water courses, and many sites are occupied.
Because responsible statistical data is usually accorded unqualified credence, it is without undue hesitation that the following bit of astonishing information, gleaned from a reliable source, is here set down as positive proof of the excellence of Loudoun's climate: "It (Leesburg) is located in a section the healthiest in the world, as proven by statistics which place the death rate at 8-1/2 per 1,000, the very lowest in the table of mortality gathered from all parts of the habitable globe."
The climate of Loudoun, like that of most other localities, is governed mainly by the direction of the prevailing winds, and, to a limited extent, is influenced by the county's diversified physical features.
Though the rainfall is abundant, amounting annually to forty or fifty inches, ordinarily the air is dry and salubrious. This ample precipitation is usually well distributed throughout the growing season and is rarely insufficient or excessive. The summer rainfall comes largely in the form of local showers, scarcely ever attended by hail. Loudoun streams for the most part are pure and rapid, and there appears to be no local cause to generate malaria.
In common with the rest of Virginia the climate of Loudoun corresponds very nearly with that of Cashmere and the best parts of China. The mean annual temperature is 50° to 55°.
Loudoun winters are not of long duration and are seldom marked by protracted severity. Snow does not cover the ground for any considerable period and the number of bright sunny days during these seasons is unusually large. In their extremes of cold they are less rigorous than the average winters of sections farther north or even of western localities of the same latitude. Consequently the growing season here is much more extended than in either of those sections. The prevailing winds in winter are from the north and west, and from these the mountains afford partial protection.
The seasons are somewhat earlier even than in the Shenandoah Valley, just over the western border of Loudoun, and the farmers here plant and harvest their crops from one week to ten days earlier than the farmers of that region.
Loudoun summers, as a rule, are long and agreeably cool, while occasional periods of extreme heat are not more oppressive than in many portions of the North. The mountains of Loudoun have a delightful summer climate coupled with inspiring scenery, and are well known as the resort of hundreds seeking rest, recreation, or the restoration of health. This region, owing to its low humidity, has little dew at night, and accordingly has been found especially beneficial for consumptives and those afflicted with pulmonary diseases. The genial southwest trade winds, blowing through the long parallel valleys, impart to them and the enclosing mountains moisture borne from the far away Gulf of Mexico.