Milk River has an average of 192 frost free days per year. It receives 34 cm of annual precipitation, 26 cm of the total coming in the form of rainfall. Annual snowfall is an average of 160 cm.
|Seasonal Mean Average Temperatures|
|January||-7 C||19 F|
|April||12 C||54 F|
|July||26 C||79 F|
|October||14 C||57 F|
The warm westerly winds (also known as a Chinook) tend to melt any snowfall throughout the winter.
The climate statistics given above are a 30 year average.
About 85 million years ago, a huge inland sea covered the middle of North America. The location of Writing-On-Stone, on the Milk River, would have been located on this very large and stormy sea. Sand was deposited on the shore which, over millions and millions of years, slowly compacted to become sandstone rock. This became part of the Milk River Formation.
Over millions and millions of years, the beach on the Late Cretaceous Inland Sea became buried. The weight of the material covering this sand compacted it into hard sandstone rock. This sandstone is evident where the Milk River Formation is exposed.
The Milk River Formation has three main components:
- Deadhorse Coulee Member
- Virgelle Member (Upper and Lower)
- Telegraph Creek Member
The Virgelle Member of the Milk River Formation consists of magnificent sandstone cliffs. Upper Virgelle, being softer, is characterized by the presence of impressive hoodoos. Lower Virgelle, bottom of the cliffs, is characterized by relatively dense (hard) rock on which there is native rock art.
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