March is the fourth coldest month.

March 23. 

2 P. M. — 40°; rather windy.

Small dark-based cumuli spring clouds, mostly in rows parallel with the horizon. 

I see one field which was plowed before the 18th and spring rye sowed. The earlier the better, they say. Some fields might have been plowed earlier, but the ground was too wet. Farmer says that some fifty years ago he plowed and sowed wheat in January, and never had so good a crop. 

I hear that Coombs has killed half a dozen ducks one of them a large gray duck in Goose Pond. He tells me it weighed five and a half pounds, — while his black ducks weigh only three and a half, — and was larger than a sheldrake and very good to eat. Simply gray, and was alone, and had a broad flat bill. Was it the gadwall? or a kind of goose? 

It will be seen by the annexed scrap [Tables from the Patent Office Reports, 1853, p.332; 1854, p.427; 1855, p.375.] that March is the fourth coldest month, or about midway between December and November. The same appears from the fifteen years' observation at Mendon. (“American Almanac,” page 86.) 

The descent to extreme cold occupies seven months and is therefore more gradual (though a part of it is more rapid) than the ascent to extreme heat, which takes only five months. 

The mean average temperature of the coldest month (February) being 23.25, and of the warmest (July) being 72.35, the whole ascent from extreme cold to extreme heat is 49.10°, and in March (32.73) we have accomplished 8.48°, or a little less than one sixth the ascent. (According to the Mendon fifteen years ' average the whole ascent is 47.5, and in March we have advanced 9.2, a little more than one fifth.) 

It appears (from the scrap) that December, January, and February, the three winter months, differ very little in temperature, and the three summer months and September are next most alike, though they differ considerably more. (Same from Mendon tables.) 

The greatest or abruptest change is from November to December (in Mendon tables from September to October), the next most abrupt from April to May (in Mendon tables from March to April). 

The least change (according to the above tables) is from December to January. (According to Mendon tables, the same from December to January as from January to February.) 

The three spring months, and also October and November, are transition months, in which the temperature rapidly changes.

H. D. Thoreau, Journal, March 23, 1860

March is the fourth coldest month. See March 25, 1860 ("To speak of the general phenomena of March")