The first half of June is cooler than the last half of May.

June 23. 

River at 7 a.m. fifteen inches above summer level, having fallen. 

A sparrow's nest with three fresh eggs in a hollow of a willow, two and a half feet from ground, at my boat's place. The bird has the usual marks, except perhaps the spot on the breast is more obvious, and the lines over the eyes more white and distinct. The eggs have a much bluer-white ground than those I have, and beside are but slightly spotted with brown except toward the larger end. The chip of the bird is metallic, not the hoarse chip of the spring song sparrow. Vide eggs in collection. 

2 p. m. — To Bare Hill road. 

This is a decidedly dogdayish day,* foretold by the red moon of last evening. The sunlight, even this fore noon, was peculiarly yellow, passing through misty clouds, and this afternoon the atmosphere is decidedly blue. 

I see it in the street within thirty rods, and perceive a distinct musty odor. First bluish, musty dog-day, and sultry. Thermometer at two only 85°, however, and wind comes easterly soon and rather cool.

The foliage is now thick and for the most part dark, and this kind of weather is probably the result of this amount of shadow; but it grows cooler with easterly wind before night.

I suspect that it may be true, as said, that the first half of June is cooler than the last half of May, on this account.

Smilacina racemosa, how long? 

Agrostis scabra, pond path at east end of Walden.

Poa compressa may fairly begin on the railroad at Walden; also piper grass just begun. 

I see a young Rana sylvatica in the woods, only five eighths of an inch long. Or is it a hylodes ? — for I see a faint cross-like mark on the back and yet the black dash on the sides of the face. 

At 7 p. m. the river is fifteen and three fourths inches above summer level. It rained hard on the 20th and part of the following night, — two and one eighth inches of rain in all, there being no drought, — raising the river from some two or three inches above summer level to seven and a half inches above summer level at 7 a. m. of the 21st. 

At 7 p. m. of the 21st, 11 inches above summer level. 

At 7 p. m. of the 23rd, 15 3/4 inches above summer level. 

Thus two and one eighth inches of rain at this season, falling in one day, with little or no wind, raises the river while it is falling some four inches; on the next day it rises four more; the next night it rises seven sixteenths inch more; the next day (second after the rain) it rises three and three sixteenths inches ; the next night it falls one eighth of an inch; it rises again three fourths of an inch, or five eighths absolutely; i. e., it rises still the third day after the rain. 

That is, after a remarkably heavy rain of one day it does not rise as much in a night as it ordinarily falls in a day at this season.

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

A sparrow's nest with three fresh eggs in a hollow of a willow, two and a half feet from ground. The eggs have a much bluer-white ground than those I have, and beside are but slightly spotted with brown except toward the larger end. See May 21, 1852 ("A song sparrow's nest and eggs so placed in a bank that none could tread on it; bluish-white, speckled."); June 13, 1858 ("I see a song sparrow's nest here in a little spruce . . . Some of the eggs have quite a blue ground."); June 14, 1855 ("A song sparrow’s nest in ditch bank under Clamshell, of coarse grass lined with fine, and five eggs nearly hatched and a peculiar dark end to them.") See also  A Book of the Seasons,  by Henry Thoreau, The Song Sparrow

This is a decidedly dogdayish day, See June 23, 1853 ("Looking down on it through the woods in middle of this sultry dogdayish afternoon, the water is a misty bluish-green. "); June 23, 1859 ("A foggy, Cape-Cod day, with an easterly wind.")

I see a young Rana sylvatica in the woods, only five eighths of an inch long. Or is it a hylodes ? — for I see a faint cross-like mark on the back and yet the black dash on the sides of the face.  Compare  August 10, 1858 ("I notice several of the hylodes hopping through the woods like wood frogs,. . . They are probably common in the woods, but not noticed, on account of their size, or not distinguished from the wood frog. I also saw a young wood frog, with the dark line through the eye, no bigger than the others. One hylodes which I bring home has a perfect cross on its back"). See September 12, 1857 ("There was a conspicuous dark-brown patch along the side of the [wood frog's] head, whose upper edge passed directly through the eye horizontally, just above its centre, so that the pupil and all below were dark and the upper portion of the iris golden") See also A Book of the Seasons,  by Henry Thoreau, The  Wood Frog (Rana sylvatica)