Laudator Temporis Acti

Oxford English Dictionary (OED), s.v. blizzard, definition 2:

A furious blast of frost-wind and blinding snow, in which man and beast frequently perish; a 'snow-squall'. Also attrib. and Comb. orig. U.S.

The earliest citations in the OED are:

1859 L.B. WOLF Diary 1 Dec. in Kansas Hist. Q. (1932) I. 205 A blizzard had come upon us about midnight... Shot 7 horses that were so chilled could not get up. 1876 Monthly Weather Rev. Dec. 424 The very severe storms known in local parlance as 'blizzards' were reported on the 8th as prevailing in Iowa and Wisconsin. 1880 Let. 29 Dec., fr. Chicago in Manch. Even. News, 24 Jan. 1881 The thermometer was 17 degrees below zero last night, and it was blowing a blizzard all the time. 1881 Standard 22 Jan. 5/1 The region [Manitoba] is swept by those fearful blasts known as 'blizzards' which send the 'poudre', or dry snow, whirling in icy clouds. 1881 N.Y. Nation 184 The hard weather has called into use a word which promises to become a national Americanism, namely 'blizzard'. It designates a storm (of snow and wind) which men cannot resist away from shelter. 1882 Contemp. Rev. Sept. 350 Those bitter 'blizzards' so justly dreaded by all who have to do with live stock. 1888 T. WATTS in Athenæum 18 Aug. 224/2 By Ferrol Bay those galleys stoop To blasts more dire than breath of Orkney blizzard.

The Merriam-Webster New Book of Word Histories (Springfield: Merriam-Webster Inc., 1991), s.v. blizzard, pp. 50-51 (at 51):

The earliest printed citation for the use that is so far known appeared in the Estherville, Iowa, Northern Vindicator on 23 April 1870. It was spelled blizards, and was cautiously enclosed in quotation marks. One week later, in the 30 April edition, it appeared again, with the now familiar double -z spelling, but still in quotation marks....The Dictionary of Americanisms has citations dated 1859 and 1861 from a diary published in the Kansas Historical Quarterly in 1932. The diary was kept by an army captain at Fort Leavenworth, Kansas. It turns out, however, that the diarist revised or enlarged or rewrote the diary about 1905, when blizzard was a common word, and we do not know whether he unconsciously used it in his revision, or if he had used it in the original, which was unfortunately thrown away. No printed evidence, however, has yet been found that antedates the Northern Vindicator.

An example of blizzard meaning snow storm, earlier than any of those cited above, is C.A. Wean, A Winter in the Pine Woods (Chicago: Wean & Shover, 1839), pp. 214-215:

The fire crackled and roared even louder than the storm outdoors, but it was a cheery, agreeable roar, which robbed the other of its terrors. A Northern Michigan blizzard, without a fire, would / have some very real terrors too.