Page:Weather Facts and Predictions.djvu/21

 other particular place the average temperature for the middle of each month at such place may be obtained approximately from the following-table:—

—and proportionally for periods intermediate between the 15th of each month.

Since wind drives away saturated air, and so causes dry air to take its place, evaporation is greater in windy than in calm weather.

A rise in the dew-point from morning to noon will be followed by rain: a fall by fine weather.

The evening dew-point generally determines the mean temperature of the night. If, therefore, this be ascertained, the approach of low temperature or of a frost at night may be seen and provided against.

A high evening dew-point indicates, if the dry bulb does not fall much, that the next day will probably be warm, but a high evening dew-point with a chilly air and a S.W. wind is rather a presage of rain.

Damp air is a much better conductor of heat than dry air, consequently it feels colder than dry air of the same temperature, because it conducts away more rapidly the heat from our bodies.

The difference between the dry and wet