Along the Atlantic Coast the greatest daily range within a month does not often exceed 30 degrees; and the average monthly range is not far from 20 degrees. Away from the coast belt daily ranges above 40 degrees are common. In the Plateau Region of the western highlands the average of daily ranges in June varies from 40 degrees to 50 degrees. At Pacific Coast stations the average daily range is not far from 15 degrees. In Arizona, a part of the Plateau Region, owing to dry air and altitude, the daily ranges have usually been greater than in most other parts of the United States. At Florence, Arizona, a daily range of 63 degrees has been recorded, and ranges above 45 degrees are noted occasionally.
Undoubtedly the greatest daily ranges occur in the high desert plateaus of Asia. The temperature records for this region are few in number, and not always trustworthy. One fact, however, has been established beyond reasonable doubt: excessively hot days are sometimes followed by freezing temperature at night.
Excessive extremes are characteristic of inland regions; and in Siberia, where inland distances are greater than in the American continent, the extremes of temperature are also greater. At Verkoyansk a minimum of −96° F has been noted; and at Wargla, a caravan station in the Sahara, a maximum of 127° F has been reported by a trained observer.[1] In the northern part of the United States, a temperature of −30° accompanying a cold wave, is not uncommon.
In the United States, the highest official temperature record, 134°, is reported at Greenland Ranch, California; the lowest, −67°, at Poplar River, Montana. It seems certain that desert regions in low latitudes are the hottest places in the world.
Temperature Normals.—The daily normals of a station are the averages of each day of the year for a period of not less than ten years. The monthly normal is the average for the particular month for not less than the same length of time; the yearly normal is computed from an average of the monthly normals. It is the custom of Weather Bureau stations to extend the computation of the means to the end of succes-
- ↑ If the figures are authentic, the absolute range for the earth, so far as is known, is 217 degrees.
