Climate of North Dakota

Wind

Wind is air in motion relative to the earth's surface. Air in motion does not move in a horizontal straight line, but moves upward, downward and sideways. Usually, however, the component of wind horizontal to the earth's surface is much larger than any other component. This is why wind is usually thought of as moving horizontally and why only the horizontal component of wind is normally measured and reported.

The average wind speed in North Dakota is greatest in late winter and early spring and least in summer (Table 12). Average wind speeds in the Red River Valley are 10 to 20 percent higher than in the rest of the state.

Table 12. Average wind speed and prevailing directions and the extreme mile of wind for Bismarck, Devils Lake, Fargo, and Williston.

Month	Bismarck			Devils Lake			Fargo			Williston
Month	Mean Speed	Prevailing direction	Fastest Mile	Mean Speed	Prevailing direction	Fastest Mile	Mean Speed	Prevailing direction	Fastest Mile	Mean Speed	Prevailing direction	Fastest Mile
January	10.2	WNW	54	9.7	NW	41	13.2	SSE	62	9.9	W	70
February	10.2	WNW	54	9.9	NW	54	13.0	N	56	9.1	NE	66
March	11.4	WNW	65	10.6	NW	54	13.6	N	56	10.1	NW	52
April	12.8	WNW	63	11.3	NW	47	14.9	N	68	11.4	SE	56
May	12.5	SSE	66	10.7	NE	52	13.8	N	72	11.9	SE	56
June	11.3	WNW	66	9.5	SE	50	12.2	SSE	115	9.7	SE	61
July	9.8	SSE	72	8.4	NW	56	10.9	S	60	9.1	SE	64
August	10.0	E	72	8.5	SE	47	11.4	SSE	71	10.1	SW	47
September	10.5	WNW	66	9.3	NW	46	12.5	SSE	88	10.1	SW	50
October	10.4	WNW	61	9.9	NW	47	13.1	SSE	57	10.0	SW	57
November	10.6	WNW	67	10.1	NW	57	13.7	S	66	9.2	SW	47
December	9.8	WNW	61	9.3	NW	42	12.8	S	58	9.7	SW	56
Year	10.8	WNW	72	9.8	NW	57	12.9	N	115	10.0	SW	70
Yrs. of record	30	14	30	57	57	57	28	14	29	5	3	8

The fastest wind speed clocked over a one-minute period at the four National Weather Service Stations in the state was 115 miles per hour. This wind speed, which greatly exceeds the threshold value of 75 miles per hour for hurricanes, was recorded when a powerful thunderstorm struck Fargo during midafternoon on June 9, 1959. The next strongest wind speed of 88 mph was also recorded at Fargo on September 1, 1960, when a line of thunderstorms moved through the city. With the exception of these two instances at Fargo, the fastest wind speeds registered over a one-minute period were about the same in winter as in summer. This indicates that winter cold fronts and low pressure systems can produce winds of about the same speed as those associated with summer thunderstorms. In addition, high winds in winter can be sustained over a period of several hours, and in rare cases two to three days, while in summer the duration of the strong winds is usually on the order of a few minutes.

In Figure 52, wind roses show the percentage of time that the winds blow from 16 compass points at Fargo, Bismarck and Minot. The five wind roses for each station cover the four seasons and an annual composite.

On an annual basis, the prevailing wind flow at Fargo shows strong incoming north and north-northwest flow and a strong south and south-southeast return flow. Wind from an easterly or southwesterly direction occurs much less frequently than from other directions. Winds at Bismarck prevail most often from a west-northwest direction, and contrary to Fargo and Minot a sizable east wind component occurs. Minot winds are more evenly balanced around the compass than Fargo or Bismarck, although northwest winds definitely prevail.

The seasonal wind roses for January, April, July and October are similar to the annual wind roses (Figure 52). Seasonal wind roses differ from the annual wind rose nearly always because the wind so often changes direction, rather than a change in the prevailing wind pattern.

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