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What's the Weather?—Using Natural Cues to Predict the Weather
Plants & Gardens News | Volume 21, Number 3 | Fall 2006/Winter 2007
by Ilene Sternberg
Illustration by Peggy Fussell
What do shepherds, sailors, farmers, and gardeners have in common? Okay, don't strain your brain too hard on this one. There's no prize money involved. Give up?
Well, since the beginning of civilization, and perhaps earlier, these folks, whether sensibly or naively, have relied on signs in nature to predict weather. Drought, storms, and hard winters have been a constant concern for these people, and they have used observations of the heavens and living organisms as guidance for when to go outside and be about their business, or when to batten down the hatches. Turns out, much of it does make sense, and modern technological tools, with only a 50- to 60-percent accuracy rate, are not much more reliable than the instruments of Mother Nature.
Proverbial Lore and the Skies
Weather lore has been passed down through the generations in hundreds of old saws, like this English proverb: "Red sky at night, sailors delight, red sky at morning, sailors take warning." This is based on a Biblical passage wherein Jesus says, "When it is evening ye say, it will be fair weather: for the sky is red. And in the morning it will be foul weather today: for the sky is red and lowering." Scientifically, a red sky at dusk happens when the sun shines through dust particles that are being pushed ahead of a high-pressure system bringing in dry air. A daybreak red sky is also due to the sun shining through dust, but the dust is now being stirred up by an approaching low-pressure system bringing moisture. (See, even in the upper atmosphere they forget to dust.)
However, don't mistake a red sky in the morning for a red sun in the morning: If the sun itself is red and the sky is a normal color, the day will be fair. Or maybe just stay in bed until midday if this is too confusing. That's what I do.
Another aphorism, "Rainbow in the morning, shepherd's warning; rainbow at night, shepherd's delight," also holds true. Rainbows occur when sunlight coming from behind the viewer reflects off raindrops to the viewer at a certain angle (around 42 degrees)—an angle the sun only makes in the morning or evening. Moreover, most rain clouds move from west to east. Thus, a rainbow in the western sky in the morning indicates approaching rain, while an afternoon rainbow presages good weather (or, more precisely, indicates the departure of rain). The rainbow-shepherd connection probably developed out of the need to keep sheep dry to avoid shrinkage and may also explain why wool comes in so many colors. (Okay, so I made up that last part.)
How about, "Ring around the sun or moon means rain or snow is coming soon"? It seems this adage is pretty accurate too. The appearance of a halo or ring around the moon is due to high-level cirrostratus clouds, which typically precede moisture-bearing low-pressure systems. These clouds also contain light-refracting ice crystals, which give the impression of a ring. By counting the number of stars in the ring, supposedly you can predict how soon rain or snow will arrive. Each star is said to represent approximately 12 to 24 hours. Of course, it's tough getting close enough to count stars, unless you have a high-powered telescope or some leftover drugs from the sixties.
Clouds are pretty accurate weather gauges—each cloud type forms due to specific activity in the atmosphere building up to a certain type of weather. "Mare's tails and mackerel scales make tall ships carry low sails" is a seafarer's maxim. "Mare's tails" are cirrus clouds; found high in the atmosphere, these clouds are pulled into long streamers resembling a mare's tail. "Mackerel scales" are altocumulus clouds, which are medium altitude and look like parallel bands or patches of small, scalelike cells. Both cloud types indicate high winds or an approaching frontal system. Sailors on tall-masted ships noticing these clouds would lower their topsails to prevent the masts from blowing over or the rigging from getting damaged.
Cues From Plants and Bugs
Plants can foretell the weather, too. Rhododendrons close their leaves when cold weather approaches, completely contracting at 20°F. As temperatures rise, leaves begin to unfurl, reopening fully at 60°F. Dandelions, bindweed, clover, wild indigo, and tulips all fold their petals before rain. Mushrooms abound in moist weather, as do mosses. Exposed seaweeds on rocks swell and rejuvenate in the high humidity just before rain.
Insects reportedly have built-in weather-detecting devices. Supposedly, a cricket can be an accurate thermometer. Count the number of chirps you hear in 15 seconds, add 37, and you have the temperature where he is sitting. (I have not tested this, since I'm rarely near a stationary cricket with a thermometer in my hand. This also works best, I imagine, if the cricket has at least some basic math skills.) Some other insect publicity stunts you can investigate: Crickets chirping loudly indicate a pleasant day to follow; spiders will spin thicker, bigger webs when weather will be dry; and when you hear the first cicada of the summer, expect fall's first frost in 90 days.
One unflappable prognosticator, scooting around town shopping for winter shelter in fall is the larval form of Pyrrharctia isabella, the Isabella tiger moth, or woolly bear caterpillar. Superstition holds that the wider the black bands on the caterpillar, the more severe will be the coming winter. The little larva is not really woolly, but rather covered with short, stiff bristles. There are 260-odd species of North American tiger moth, some with no bands and others with bands of naturally varying sizes. Some entomologists attribute the relative amounts of Isabella's red and black to temperature and moisture variations during its early life—they go through six larval stages (the woollies, that is, not the entomologists). Other bug experts claim band width is determined by the caterpillar's age (i.e., how late it emerged in the spring), in which case this might be indicative of a harsh winter or an early spring, but it would refer to the previous year, not the one to follow.
In any event, between 1948 and 1956, Dr. C.H. Curran, curator of insects at the American Museum of Natural History in New York City, began studying the precision of woolly bear predictions at—where else?—Bear Mountain State Park, in New York. Annual segment counts and winter projections were resurrected there in 1988 and continue today. The woolly bears were declared 80 percent accurate!
Animal Instincts
Those among us of a certain age can count on another signal: arthritis pain. Decreasing atmospheric pressure causes bodily gases to expand, thus triggering aching joints. (Barometric drops also cause other phenomena: Fetid marshland smells become more acute as trapped methane is released into the air; distant objects appear closer and more sharply focused as dust particles begin to settle to the ground; and smoke hangs low, rather than rising into the air.) So always trust your throbbing bunions' admonition that the weather is turning bad.
Other animals also play meteorologist sometimes. Dogs and cats can purportedly sense when a tornado or earthquake is coming. Birds and bats tend to fly lower before rain. This is thought due to the "thinning" of the air during pre-storm low-pressure conditions; that is, they prefer to fly where air is most dense so they can get greater lift with their wings. Some references contend that birds and bats fly lower to ease the pain in their ears due to the decreased barometric pressure. It's hard to prove this, however—they may be merely cowering from the screech of millions of televisions simultaneously tuned to American Idol. The Gardener's Weather Bible, by Sally Roth (Rodale), debunks the myth that animals grow thicker coats in preparation for a bad winter, saying that luxuriant coats merely result from a summer of abundant "eats." And as for that pampered Punxsutawney Phil—the celebrity groundhog who nets his hometown a cool $3 million per annum, has a personal income of about $30,000, and double-digit entourage of PR people—he is hardly deserving of the attention he gets. Each February 2, hordes huddle to interpret whether Phil sees his shadow (a portent of six more weeks of rough winter); but despite what his fan club says, he has only been right 25 to 39 percent of the time.
The Old Farmer's Almanac has its own rather complex formula for long-range forecasting and can claim 80 percent reliability since its debut in 1792. And in case you'd like to try it, the almanac also offers these detailed instructions at "How to Predict the Weather Using a Pig Spleen."
Ilene Sternberg is an award-winning garden writer and the author of Best Garden Plants for Pennsylvania (Lone Pine Publishing).