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General Remarks-- Temperature—Extremes of Heat and Cold—'Winds—The Sea BreezeNorthers—Southeasters—Rains—Storms—Cloud and Mist—Snow and hail —Thunder and Lightning—Relations of Climate to Agriculture and other S Health, Domestic Economy, etc.
In this outline of the climate of California minute details and the scientific investigation of causes are avoided, and a practical view of the subject is presented to the reader, with especial relation to the capacities of the country, and the comforts and industries of the people.
The climate of California is too much varied to be considered as a whole. It might be regarded almost as a heterogeneous mixture of the tropical and the arctic. From the Capital city, under the noonday sun of the summer solstice, with a temperature of from 90 to 100°, exceeding the extreme summer heat of the Atlantic States, you will see the snows glistening on the Sierras at no great distance. And by taking the cars on the trans-continental railroad, a few hours of travel will transport you to an arctic landscape. On the other hand, embarking on the steamer for San Francisco, at two o'clock in the afternoon, and travelling in the opposite direction, before night you are shivering in the cold sea breeze which sweeps up the bay.
It is not necessary to journey so far in order to experience the same transition. You have only to cross any of the mountain walls which separate the ocean and bay from the interior, and which dam out the cold ocean atmosphere.
There are essentially two climates in California, the land climate and the sea climate. The latter derives its low temperature from the ocean, the water of which, along the coast, stands at from 52° to 54°, all the year round. The evenness of the ocean temperature is owing to a steady current from the north, which is accompanied also by winds in the same direction during the entire summer season, or rather from April to October inclusive. Almost daily, during this period, a deluge of cold, damp air, of the same temperature as the ocean over which it has passed, is poured upon the land. It is mostly laden with mist, in dense clouds, which it deposits at the foot-hills and on the slopes of the highlands, or carries a short distance into the interior wherever there is a break in the land-wall.
The land climate is as nearly as possible the opposite in every respect. In summer and autumn it is hot and dry. It undergoes various modifications from the configuration of the surface of the earth. Even the mountains, which retain the snow till a late period, present a high temperature in the middle of the day; and the presence of snow on their summits in June is owing to the great mass which has accumulated on them, rather than to cold weather.
A large district of territory lies between the jurisdiction of the two climates, and subject to their joint influence. It is composed chiefly of valleys surrounding the bay of San Francisco, and penetrating into the interior in every direction. There is no climate in the world more delightful than these valleys enjoy, and no territory more productive. Whilst the ocean prevents the contiguous land from being scorched in summer, it also prevents it from being frozen in winter. Hence, ice and snow are not common in the ocean climate. The difference in temperature is comparatively slight between summer and winter.
The cold of winter in the interior is not intense, even on mountain elevations, with the exception of the tier of counties in the extreme north. Its degree depends much, however, on the altitude of the locality. The severity of winter is due, not to extreme cold, in any part of California, but to violent and prolonged snow storms in one section, and cold and prolonged rains in others.
It is interesting to cast the eye over the map of the State, and trace out climatic modifications as governed by topography. First, look at the long range of coast, the slope of which, as far back as the first mountain wall, is under the control of the ocean, and has the most uniform of climates. It is a narrow strip of territory, the only part of the State preserved from desiccation in summer by daily showers of mist, and, therefore, admirably adapted to dairy purposes. Then survey the counties bordering on the great bay—Sonoma, Napa, Solano, Contra Costa, Alameda, Santa Clara and San Mateo, borrowing one half their climate from the ocean and the other half from the interior; inexhaustible in agricultural resources, and forming the granary of the Pacific. The Pajaro and some other valleys farther south, to which the sea winds gain access, belong to the same system; and those also of the Sacramento and San Joaquin, although in a lesser degree, being farther removed from the ocean. Then regard the mountain region, with its countless little valleys, buried up with snow in winter, bursting forth into a paradise with the spring, and converted into furnaces by the summer's sun, and yet luxuriant with all kinds of delicious fruits. In this section are concentrated the mining interests. Finally, view the southern section, embracing one fourth of the State, removed alike from both extremes which operate in the north, controlled neither by mountain nor ocean, and enjoying the most genial temperature—a section of country wanting only in the certainty of winter rains to make it an Eden.
After these general remarks, let us proceed to a more definite view of the subject, taking the climate of San Francisco as a stand-point and basis of comparison. This is proper, not only because the metropolis is the center of population, containing one fourth the inhabitants of the State, but because its climate is a type of that of the coast and bay regions. We will first consider the temperature.
TEMPERATURE—EXTREMES OF HEAT AND COLD.
The record of the climate of San Francisco, as kept by Dr. Henry Gibbons, extending from the autumn of 1850 to January, 1868, a period of seventeen years, shows the coldest weather during that time to have occurred in January, 1854, when the mercury fell as low as 25°. The coldest noonday for the same period was 37°. Persons who do not rise early may see no ice in that city for several years in succession. When it is cold enough to preserve ice in the shade all day the circumstance is noted as a phenomenon. It is not uncommon for the entire winter to pass away without bringing the thermometer down so low as the point of freezing. In the year 1853 it fell at no time lower than 40°, or eight degrees above the freezing point.
The extreme of heat in the same period occurred on September 10th and 11th, 1852, when the thermometer reached 97° and 98° on the two days respectively. This, however, was entirely exceptional, and might not again occur in half a century. The air was dry as a sirocco, and had a curious effect on the wood-work of houses, causing a constant crackling noise, from the shrinking of the timber, and the plaster breaking on the wooden partitions. In a locality somewhat exposed to reflected heat from the sun, and where the temperature was 100 \ a thermometer with a wet bulb fell to 68°—the evaporation reducing it thirty-two degrees.
With the exception just noted, the hottest day in the seventeen years -was on the 6th of July, 1867, when the thermometer stood at 93°. In October, 1864, and in September, 1865, it reached 91°; and in July, 1855, it rose once to 90°. Thus, it appears there were but six days in seventeen years when the temperature was as high as 90°, and only two of these six days were in the summer months.
The absence of warm weather in the summer months is characteristic of the coast climate and strikes a stranger forcibly. The most ordinary programme of this climate for the year is as follows, beginning with the rainy season: The first decided rains are in November or December, when the country, after having been parched with drought, puts on the garb of spring. In January the rains abate and vegetation advances slowly, with occasional slight frosts. February is spring-like, with but little rain. March and April are pleasant and showery, with an occasional hot day. In May the sea breeze begins, but does not give much annoyance. In June, just as warm weather is about to set in, the sea breeze comes daily, and keeps down the temperature. It continues through July and August, occasionally holding up for a day or two, and permitting the sun to heat the air to the sweating point. In September the sea wind moderates and there is a slight taste of summer, which is prolonged into the next month. The pleasant weather often lingers in the lap of winter, and is interrupted only by the rains of November or December.
By running the eye over the following table, a general idea can be gained of the coast climate as regards temperature. The first column represents the average temperature of each month at sunrise, for seventeen years; the second, at noon ; and the third, is the mean of the other two.
Observe, in the table, the regular increase from January to September, and the rapid decrease from October to December; nine months of increase and two of decrease. Notice, also, the uniform increase of the night temperature as represented in the first column, and the irregularity in the noonday increase, the sea breeze arresting it in May, and the sun giving it an upward impulse in June) before the sea wind has gained undisputed control.
Whilst the summer months are warmest in the interior, as in most countries, a very different arrangement exists in the coast climate. This is because the sun has entire control inland, within its mountain intrenchments, and the ocean almost entire control of the coast slope outside of those intrenchments. The two forces act inversely; that is to say, the more powerful the sun's heat in the interior, the more powerful is the pressure and force of the cold ocean atmosphere without. The heating power of the sun in the interior begins to decline after midsummer, and the temperature then begins to fall. But this lessens the draught from outside and gives the sun greater calorific power over the exterior atmosphere. Accordingly, with the diminution of the force of the sea breeze in September, comes a slight touch of summer along the coast. The sun, not having receded far from the tropic of Cancer, avails itself of every opportunity to warm up the coast, and gains a temporary triumph over the ocean in September, or sometimes not till October. Hence, as the table shows, September is the warmest month in the year, and October next; then comes August; July, the hottest month almost everywhere else, is the fourth here, or ranks as such in connection with June ; next come April and May; then March and November; then February, and finally January and December, the only winter months.
The mean annual temperature at San Francisco is 56.6, which may be set down as the mean of the coast and bay climate. As we recede from the ocean, the days are warmer and the nights colder, the sun being the great disturber of temperature, and the ocean the great equalizer. But the increase of the day corresponds so nearly with the diminution of the night temperature, that the mean varies but little within the range of the sea breeze.
Washington and Richmond, nearly in the same latitude as San Francisco, have a mean of 54 or Mk, two degrees colder than the latter. This appears, at first sight, to be a small difference; but its value is made evident by reflecting that it is a difference for every day in the year— each day of the year in San Francisco, from January to December, having an average of two degrees higher than the corresponding day on