The coldest month is January; December and February are relatively cold. The hottest months are May and June. The heat is, at all times, moderate and agreeable. The course of the temperature has all the characters of an insular climate, without having so much humidity. The oscillation of the average temperature is greatest in March and during the dry season, as at that time the sky is clear and the soil exposed to uninterrupted insolation during the day, while the earth’s radiation of heat during the night is rapid. Also the daily oscillation is considerable during the dry season, and continues during the first month of the rainy season, according to the condition of the sky. In 1890 the sun shone in San José 1911 hours, that is an average of five hours and fourteen minutes per day. February is the month of most sunshine and least nebulosity. The hour of most sunshine during the year is that between eight and nine a. m., and that of the least is in the afternoon. The oscillation of the temperature of the soil is, at a depth of one meter, 2, 13° C., per year. At a depth of three meters, the temperature of the soil is lowest in February and March, when it is 20, 48° C., and highest in August, when it is 20, 75° C. The daily variation is almost nothing during the first three months of the year, and the sky is relatively clear, while, from May to October, not one day is clear. During the hottest hours of the day the sky begins regularly to be darkened by clouds, due to ascending atmospheric currents. In San José the sky is ordinarily clear between midnight and noon, even during the most rainy months, and cloudy the rest of the twenty-four hours. Although the rainfalls are abundant here from May to October, with rare exceptions they do not last more than a few hours each day. The mornings are generally splendid and the air very pure, and nearly every day the sunset can be clearly observed. From May to November there are about two hours of copious rain daily between one and four o’clock in the afternoon, averaging, with great regularity, from ten to twelve inches a month, and from seventy to eighty inches during the year. Towards the end of June there is a short dry period called “Veranillo de San Juan.” Through the Desengaño and Palma Passes the northern rains penetrate a short distance every day, and the northern descent of the Palma towards Carillo is probably the most rainy district of the Republic. At Tres Rios, having an elevation of 4140 feet, six miles east of San José, at the western foot of the Ochomogo Pass, the rain record for 126 days out of ten months showed a fall of 100 inches, while at San José, during the same period of ten months there were 147 rainy days, with a fall of eighty-four inches. In the month of May Professor Pittier, to whom we owe these excellent data, measured nine inches in rainfall in one and one-half hours.