Among the commonest and most noticeable indications are the following, and only in very rare instances will these signs fail:
| Unusual twinkling of stars, Double horns to the moon, Halos around stars or moon, “Wind dogs” | Increasing wind, or rain with a liability of wind. |
| Wind shifting from west to east | Increase of wind from the other direction. |
| Rosy sky at sunset | Fine weather. |
| Sickly, greenish-colored sunset | Wind and rain. |
| Dark red or crimson sunset | Rain. |
| Bright-yellow sky at sunset | Wind. |
| Pale-yellow, or saffron, sunset | Rain. |
| Mixed red and yellow sunset | Rain and squally weather. |
| Remarkably clear atmosphere with distant objects standing above the water and seemingly in air | Wind, usually from the northwest, and often rain. |
| Heavy dews | Fine weather. |
| Fogs | Change in weather and little wind. |
| Misty clouds on hills, remaining stationary, increasing or descending | Rain and wind. |
| Misty clouds on hills, rising or dispersing | Fairer weather. |
| Red morning sky | Bad weather and wind. |
| Gray morning sky | Fine weather. |
| High dawn (dawn seen above a bank of clouds) | Wind. |
| Low dawn (daylight breaking close to the horizon) | Fair. |
| Soft, delicate clouds | Fair and light winds. |
| Hard-edged, oily clouds | Wind. |
| Dark, gloomy sky | Windy. |
| Light, bright sky | Fine weather. |
| Small, inky clouds | Rain. |
| Light “scud,” or small clouds moving across heavier clouds | Wind and rain. |
| Light, scudding clouds by themselves | Wind and dry weather. |
| High, upper clouds scudding past moon or stars in a different direction from the lower cloud-masses | Change of wind. |
| After fine weather a change is indicated by light streaks, wisps, or mottled patches of distant clouds which increase and join. A haze which becomes murky and clouds the sky also indicates a change to bad weather. | |
| Light, delicate colors, with soft-edged clouds | Fine weather. |
| Brilliant, or gaudy, colors and sharp, hard-edged clouds | Rain and wind. |
| A mackerel sky (small, separate, white clouds covering the sky) | Wet weather. |
| “Mares’ tails” (long, wispy, curved, isolated clouds against a blue sky) | Wind. |
| Rainbow early in the morning | Bad weather. |
| Rainbows in afternoon | Fair. |
Many of these weather indications have become so widely known and universally recognized by seamen that they have been put into doggerel verse to make them more easily remembered and every boat sailor should learn these, for nine times out of ten they will prove true.
If wind shifts against the sun,
Trust it not, for back ’twill run.
* * *
Mackerels’ scales and Mares’ tails,
Cautious sailors shorten sails.
* * *
A mackerel sky