Climate of North Dakota

Relative Humidity

Relative humidity is the most commonly used measure of atmospheric moisture. Relative humidity is the ratio of the actual amount of moisture in the air to the amount of moisture that the air could hold if saturated at that temperature. The amount of moisture that air can hold depends upon temperature. Warm air can hold more moisture than cold air. Large daily changes in relative humidity can take place without any change in absolute moisture content of the air. For example, 100 percent relative humidity at a temperature of 65 degrees during the early morning hours will drop to about 46 percent in the afternoon if the air temperature rises to 95 degrees. Because of this temperature influence, relative humidity is lowest during the warmest portion of the day and highest during the coolest hours of night and very early morning.

Comparison of average relative humidity data at six-hour intervals in Table 8 shows that the eastern areas of the state are more humid than the western areas. This is most easily observed in the noon and 6:00 p.m. observations. For example, average 6:00 p.m. relative humidity for the year at Fargo and Devils Lake is 62 and 63 percent, respectively, while at Bismarck and Williston the average relative humidity is only 53 and 54 percent, respectively. In some late summer and fall months, the relative humidity at 6:00 p.m. is 15 percentage points or more lower in the west than in the east. Notice also in Table 8 that relative humidity is higher at midnight and 6:00 a.m. in summer than in winter, while at noon and at 6:00 p.m. the relative humidity is much lower in summer than in winter.

Table 8. Average realtive humidity by month and for year at hour indicated at four locations in North Dakota.

Station	Time	J	F	M	A	M	J	J	A	S	O	N	D	Yr.
Bismarck	Mid	70	74	74	69	70	76	74	70	73	68	73	72	72
	6A	71	74	76	77	77	83	82	79	82	76	75	73	77
	12N	65	68	61	52	48	54	48	43	49	46	58	65	55
	6P	67	69	58	46	44	49	44	38	45	45	60	68	53
Devils Lake	Mid	NOT AVAILABLE
	6A	76	78	83	82	80	84	86	86	86	83	83	79	82
	12N	72	72	70	56	50	56	53	51	54	57	71	74	61
	6P	76	77	73	54	48	54	52	49	55	59	75	78	63
Fargo	Mid	72	75	81	78	71	77	80	77	81	78	80	77	77
	6A	72	75	82	82	79	83	86	87	88	83	83	78	81
	12N	68	70	70	62	52	58	55	53	60	60	69	74	63
	6P	71	72	70	60	48	55	53	48	58	61	72	76	62
Williston	Mid	78	82	79	69	64	73	75	64	68	77	79	80	74
	6A	76	80	82	81	77	84	84	79	81	78	81	78	80
	12N	70	71	64	54	46	52	47	45	50	51	65	70	57
	6P	71	72	61	49	41	48	41	36	42	49	67	73	54

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