#MEwx Today's Weather Proverb

“Rain before seven, clear before eleven.”

This proverb is actually more related to fog than rain, but it makes a handy little saying. The most common type of fog is called radiation fog, which occurs on clear, atmospherically stable nights. As we learned with the proverb about dew, heat from the ground radiates to outer space, cooling the ground to the dew-point temperature. This creates drew. As it cools even more, condensation is formed in the air through a process known as heat conduction. This occurrence is almost exclusively a nighttime and very early morning phenomenon.

In some cases, if the air has some turbulence, the fog can thicken and even produce rain. This isn’t rain from a low pressure system, though, meaning the vapor will soon be spent, and the rain will not last long. Hence, if there is rain early in the morning (before seven), it’s likely to clear off by lunchtime.

Note that this is only accurate for this type of fog-related shower. If it’s a true low pressure system, the rule does not apply.