Page:Weather Facts and Predictions.djvu/40

 will be a specially heavy fail of between 3 and 4 inches, and it may be said that as far as is known no part of Great Britain is free from the chances of such a visitation. As long as the diameter of the guage exceeds 3 inches it makes hardly any difference in the rain taken whether the diameter of the guage be 4 inches or 24 inches.

When the Greenwich rainfall of the first seven months of the year has been large (say 14 inches or more) the mean temperature of the following winter (December—February inclusive) will be in excess of or about the average, unless the mean of the intervening period of August—October inclusive, has been remarkably cold, in which case the latter part of the succeeding winter (say February) will present some marked extremes of cold.—(Brumham.)

Rain may be expected when the sky assumes an almost colourless appearance in the direction of the Wind, especially if lines of dark or muddy cirro-stratus lie above and about the horizon.

Thunderstorms are most frequent in the tropics and diminish in frequency towards the poles. They are more frequent in summer than in winter and in mountainous countries than in plains, during the day than during the night, and after midday than before.

Just prior to the bursting of the storm the air is exceptionally warm and stifling, and this characteristic is especially noticeable in winter and at night.