When I arrived in Northern California on a Friday in mid-January, everybody was picking up after an immense storm that had swept the state from San Francisco to San Diego with 60-knot winds and up to seven inches of rain. That night, while snuggling comfortably into a sleeping bag in the after cabin of a boat at a marina in Sausalito, I reflected on how bouncy the boat must have been only 24 hours earlier. I looked forward to good weather for the safety seminar at which I would speak the next day, and to even better weather for my hike on Sunday.
And I was right. There was hardly a cloud and not a capful of fog over the next two days. When I drove with a friend to the top of nearby Mt. Tamalpias on Sunday morning, the bay and its islands glistened in the near distance, and that afternoon’s hike out to the Pt. Bonita lighthouse was deliciously clear and cool. There was so little insulating cloud cover that when I arose before dawn on Monday to head to the airport, the air temperature was in the high 20s and the pier had a crust of ice under my skidding feet
I’m not claiming to be a weather genius. All I did was apply a common rule of thumb that says that weather works in cycles. Just as the poet George Herbert observed, "A fair day in winter is the mother of a storm," we can pretty much count on a stormy day fathering a couple of clearing days of cool, dry, and hard northwesterlies that sweep the moisture out of the air.
Watchers of weather have discovered many patterns that help them predict changes. Almost 2,400 years ago, the Greek scientist and philosopher Theophrastus, a student of Aristotle, wrote an essay, "Concerning Weather Signs," in which he laid down hundreds of rules. Some seem bizarre, for instance: "When sheep begin to breed late, it is a sign which fulfills itself in fair weather. So it is when an ox lies on his left side and also when a dog does the same." I have no idea what to make of those, yet many of his observations make sense: "When birds flee from the sea" is an indication of an approaching storm—and why not? Many storms originate at sea.
Since the time of Theophrastus, mariners have used easily remembered jingles to predict weather. Some report the appearance of clouds, for instance: "Trace the sky the painter's brush, the winds around you soon will rush." Bad weather is dramatic. Both a sky’s striking color and stormy weather may result from great differences in air temperature and humidity. Clouds are often given colloquial names reflecting their shape. High cirrus clouds are called "chicken scratches" after their fine lines or "mare's tails" for their filmy quality. Since they often precede a storm by a day or two, "Mare's tails, mare's tails, make lofty ships carry low sails." The changeable, puffy weather under fish-scaly cirrocumulus clouds inspired the saying, "Mackerel scales, furl your sails."
"In by day, out by night" neatly describes the thermal effect sequence of daytime onshore sea or lake breezes (as the land heats above the temperature of the water) followed by nighttime offshore land breezes (as the land cools below the water's temperature). A westerly or southwesterly sea or lake breeze is often said to "follow the sun," meaning that it veers (shifts clockwise, in a westerly direction) during the afternoon as the land heats up and the thermal effect increases.
Another rule of thumb helps predict sea breezes:
"When the dew is on the grass
Rain will never come to pass.
When grass is dry at morning light
Look for rain before the night."
Dew forms when the air is cooled to its dew point, when it overflows with moisture. At night this happens in clear, cloudless weather, which (as it did in Sausalito last month) allows the day's heat to escape into the atmosphere. If a cloudless night cools the air, a cloudless day heats it and creates thermals. A heavy dew at dawn, therefore, may promise a fresh sea breeze that afternoon.
In another reference to moisture, our friend Theophrastus of Athens observed the effects on wildlife of changes in barometric pressure and humidity: "When in fine weather bees do not fly long distances, but fly about where they are, it indicates that there will be a storm." Their wings are too heavy with humidity. Because humidity washes the air of dust particles and thus improves visibility, the saying "The farther the sight, the nearer the rain" often applies. And since low, dense, rainy stratus and nimbostratus clouds keep noise as well as heat from escaping into the atmosphere, "Sound traveling far and wide, a stormy day will betide."
Finally, we have an old friend:
"Red sky in morning,
Sailor take warning.
Red sky at night,
Probably the most famous of all weather sayings, it may be one of the oldest (a version can be found in St. Matthew’s gospel). As I understand the phenomenon it speaks for, a sharply defined red sunset or dawn is caused by sun rays shining through dry, dusty air. In the evening, the clear red sunset is to the west of the observer. Because weather systems usually move from west to east, good weather is here or on the way. But the red sun of dawn is clear weather that has moved east, and (given the usual three- to five-day weather cycle) odds are that wet weather is overhead or imminent. Another version of this saying goes: "Evening red and morning gray, send the sailor on his way."
May your mornings, therefore, be gray (not black) and your evenings red and calm. If you’re aware of other traditional sayings or poems about the weather, send them along, I’d be interested to see them.