A wet summer is always followed by a frosty winter; but it happens
occasionally that the cold extends no farther. Two remarkable instances
of this occurred in 1807-8 and 1813-14. With these exceptions, every
frosty winter has been followed by a cold summer.
The true cause of cold, or rather the direct cause, is to be found in
the winter excess of west wind, every winter with excess of west wind
being followed by a cold summer; and if there is no cold before, or
during a first excess, then a second excess of west wind in winter
occasions a still colder summer than the first. It also appears, by
repeated experience, that cold does not extend to more than two years at
a time.
Again, if the winter excess of east wind be great, in the first
instance, the winters will be mild, and followed by mild summers; while
the summer excess of east wind is itself, in the first instance, always
mild; but uniformly followed by cold winters and cold summers, which
continue, more or less, for one or two years, according to
circumstances.--_Mackenzie, Syst. of the Weather_.
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