Page:Weather Facts and Predictions.djvu/37

 down a considerable quantity of rain, if the barometer be watched from the time of the cloud's appearance in the W., to its appearance in the E., it will be observed to fall a little and then to recover its original level, the fall being quite a local one.

A steady continuance of rain is usually preceded by fair weather.

If after rain seems imminent several days of fine weather occur, it is certain that the condition of the air has undergone change; that the aqueous vapour has been driven off before it had time to condense. A change of wind will accompany such a general change.

If much rain from the S. is followed by fine weather for a week, the wind remaining S., a prolonged absence of rain may be expected.

Rain usually comes from the W. A clear sunset is therefore a proof that no rain is imminent from that quarter nor probably very near from any quarter.

In winter rain with a W. wind and a rising barometer turns to snow.

Sudden rains do not last long, but when the sky thickens gradually and the heavenly bodies grow more and more dim, rain of some duration may be looked for.

If it begins to rain before sunrise the rain may cease by about noon; but if the rain commences after the sun has risen it is likely to last all day, unless it should be preceded by a rainbow.

A heavy shower after the commencement of a gale of wind indicates an approaching calm.