National Geographic : 1890 Jul
The IrrigationProblemin Montana. 219 The remaining 10,000,000 acres may be classed as barren and rugged mountain peaks and some little barren "bad lands" near the southeastern corner of the State, and the broken and rough cut banks of rivers, "coulees," etc. It is in these more rugged mountain regions that the great gold, silver and copper deposits are found. CLIMATE. The climate of Montana is far more moderate and agreeable than is generally supposed, the spring and fall months in the val leys, which are the principal inhabited and cultivated portions, being delightfully mild and pleasant, with frost generally only at night, though these last till May and begin in early October. The accompanying table shows the dates of the first and last killing frosts at Helena, also the mean monthly temperature at Helena, which place is chosen as a typical station, its altitude being 4,262 feet. From this table, which extends over a period of ten years, from 1880 to 1889, inclusive, with few interruptions, it appears that the earliest killing frost occurred on September 6th, 1881, and the latest killing frost on May 3d, 1888, but these were very exceptional frosts, the average dates for the same periods being September 26th and April 26th. The maximum temperature during the same period occurred in July, 1886, and was 103 degrees in the shade, while no other year showed a higher temperature than 97 degrees; and the average maximum tem perature for the ten years was 94 degrees. The minimum temperature for the same period was -40 degrees, occurring in February, 1887, while the average minimum for ten years was - 29 degrees. Great ranges of temperature are sometimes expe rienced, however, especially in local areas in the higher mountain valleys, where unusual frosts and snow flurries have occurred, though rarely, killing potatoes and other tender crops even in July and August. On September 5th of this year in the upper Madison Valley above 6500 feet of elevation, a temperature was experienced in the forenoon of 70 degrees, while at about 8 o'clock on the same evening, a snow squall occurred during which the thermometer must have fallen several degrees below the freezing point; by 9 o'clock on the following morning all of the snow had disappeared and the temperature had greatly moderated.