Pious people were well within their rights to thank God for the chinook, although (to be consistent) they should also have rendered thanks every morning for the rising of the sun. For, equally, the chinook and the sunrise were the result of natural processes. A week earlier the cold wave in Alberta had been associated with an approaching storm in California, not as cause and effect, but merely as the two parts of a broken cup fit perfectly, being really one. Now, in the same way, the long continuance of the storm matched the coming of the chinook.

Nevertheless, the mild and dry air now melting the snow upon the plains had a history during the past week which even by atmospheric standards was an Odyssey. On the preceding Friday, as frigid and dry polar air, it had moved from the frozen Arctic Ocean over the region of tundra west of Coppermine. On Saturday, grown even colder, it was moving west along the Yukon Valley. On Sunday, maintaining its speed of nearly eight hundred miles in twenty-four hours, it crossed the mountains of southern Alaska, became warmer and drier because of its descent, and moved southward in the region of Kodiak Island. On Monday it thrust south far into the Pacific as part of the western discharge of the polar air; over the ocean it was growing rapidly warmer and more moist. On Tuesday it felt the pull of the storm-center off the California coast and swung toward the southwest. On Wednesday the same storm brought it northeast at about the latitude of San Francisco; flung upward by the mountains, it discharged its newly gained moisture as rain and snow. On Thursday, it was again dry and moderately cold; still within the orbit of the storm, it was being driven rapidly northward as a severe wind, dry and below freezing, across the high plateau of eastern Washington; by the late afternoon it was reaching through and over the mountains of British Columbia. At this point, because of the pressure systems which were being built up, the old storm center was no longer able to hold it, and the air moved northeastward in the control of another storm just developing farther north.

Even on the mountain tops the air had been dry and only moderately cold. Descending, it had grown much warmer and drier. By daybreak temperatures from Edmonton to Regina were well above freezing. The snow had almost vanished; wide pools of water stood in the fields. Yet the streams did not rise greatly; the warm dry air sucked up the water almost as rapidly as the snow melted, and in many places evaporated the snow even before it could change to liquid. Over all the wide prairie, the saving chinook had broken the deadly grip of the north.

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