_Summer Temperature_.--The temperature in summer time must be sufficient to properly ripen the grapes, but must not be so great as to injure them either while they hang on the vines, or while they are exposed to dry on the trays. The average heat required to do the work of maturing is not exactly known, but it is certain that a very high degree is not absolutely needed to produce sweet grapes. As far as our experience goes, it seems that cool weather, with the average temperature of ninety degrees Fahrenheit, would be most beneficial in the fore part of the season, while when the grapes begin to ripen a greater heat is desirable. It is not the warmest countries nor the warmest seasons which produce the earliest grapes. Thus while the season of 1888 was in California unusually cool, with the thermometer seldom reaching one hundred degrees in June and July, the raisin season was nevertheless a very early one, and much earlier than seasons remarkable for their early high temperature. In Malaga and Smyrna, the heat seldom reaches one hundred degrees, and the grapes ripen several weeks earlier than in Fresno, where the summer temperature averages ten degrees higher. In Fresno, on the contrary, the season is earlier than in Southern California, where probably the seabreezes retard the ripening of the grapes. A temperature of over one hundred and five degrees proves injurious to unprotected or exposed grapes in the central region of California, but in San Diego county several degrees less is sufficient to scald the grapes or give them a cooked flavor if they are already exposed on the trays to dry. It is certain that with an average highest temperature of ninety degrees, the grapes develop better and become larger and sweeter than where the heat is excessive and reaches one hundred and ten degrees or more.[6] [6] Whenever the temperature is referred to it means the degree of heat (Fahrenheit) in the shade, and not in the sun except when so expressly stated. The time when the greatest temperature occurs is of practical importance. Excessive heat can be tolerated by grapes protected by leaves and branches or otherwise sheltered, but if it happens at a time when the bunches are exposed to dry on the trays, the injury to the berries will be great or even ruinous. Early localities are especially apt to suffer in this way, and it is well to experiment before too much confidence is placed in very early regions. To such places, however, there remains the possibility of curing the raisins in partial shade, as is done in Chile, thus producing raisins of an entirely different type from the Malaga or California product.