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Weather Flags

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There is an interesting set of signal flags that are (were) used as weather signals by the US Department of Agriculture. Perhaps these went out of use with the widespread use of radio in the early years of this century (or maybe they are still used? This is what "The World Almanac" (1893) had to say (my comments in square brackets):

"The weather bureau furnishes, when practicable, for the benefit of the general public and those interests dependent to a greater or less extent upon weather conditions, the 'forecasts' which are prepared at that office daily at 10am and 10pm, for the following day. These weather forecasts are telegraphed to observers at stations of the weather bureau, railway officials, and many others, and are so worded as to be readily communicated to the public by means of flags or steam whistles. The flags adopted for this purpose are five in number, and of the form and dimensions indicated below:

image by Phil Nelson

white flag, six feet square [1800mm], indicates clear or fair weather.

image by Phil Nelson
blue flag, six feet square, indicates rain or snow.

image by Phil Nelson
white and blue flag (parallel bars of white and blue)*, six feet square, indicates that local rains or showers will occur, and that the rainfall will not be general
*an accompanying picture indicates a horizontal bicolour, white over blue

image by Phil Nelson
black triangular flag four feet at the base [presumably hoist; 1200mm] and six feet in length, always refers to temperature; when placed above [previously mentioned flags] number 1, 2, or 3 it indicates warmer weather; when placed below numbers 1, 2, or 3 it indicates colder weather; when not displayed, the indications are that the temperature will remain stationary, or that the change in temperature will not vary more than four degrees [Fahrenheit] from the temperature of the same hour of the previous day from March to October inclusive, and not more than six degrees for the remaining months of the year.

image by Phil Nelson
white flag, six feet square, with black square in centre [picture suggests two feet/600mm square], indicates the approach of a sudden and decided fall in temperature. This flag is not to be displayed unless it is expected that the temperature will fall to forty-two degrees or lower, and is usually ordered at least twenty-four hours in advance of the cold wave. When number five is displayed, number four is omitted, but it may be displayed above either flag 1 or 2.

A special Storm flag, red with black square in the centre, is prescribed for use in North and South Dakota, Minnesota (except at lake stations), Iowa, Nebraska, and Wyoming, to indicate high winds, accompanied by snow, with temperature below freezing.

When displayed on poles, the signals should be arranged to read downward; when displayed from horizontal supports, a small streamer [colour unspecified] should be attached to indicate the point from which the signals are to be read."

James Dignan, 06 December 1997

Storm flags are still used and not just in the states named. They are very often found in the San Francisco Bay area to warn boats leaving the Gate for the open sea. Even the weatherman on TV has little storm flags to show the approaching storm.

Rich Hansen, 05 December 1997