Milton's Prelapsarian Paradise: Eternal Spring and Autumn, but No Summer or Winter?

Paradise (1620)

Jan Brueghel the Younger

(Image from Wikipedia)

I'm still looking into John Milton's Paradise Lost references to the seasons. He seems to use especially "spring" but sometimes "autumn" to describe prelapsarian Paradise, whereas "summer" and "winter" literally refer only to seasons after the fall.

He has the narrator refer to "eternal spring" in a description of Paradise:

The Birds thir quire apply; aires, vernal aires,
Breathing the smell of field and grove, attune
The trembling leaves, while Universal Pan
Knit with the Graces and the Hours in dance
Led on th' Eternal Spring. (PL 4.264-268)

Note that the springtime is 'eternal', as already pointed out, but autumn also is present with springtime, as we've previously seen:

. . . Rais'd of grassie terf
Thir Table was, and mossie seats had round,
And on her ample Square from side to side
All Autumn pil'd, though Spring and Autumn here
Danc'd hand in hand. (PL 5.391-395)

Presumably, "autumn" in this sense refers to ripened fruit, not a time of dead and falling leaves. What of summer, though? It receives mention here in a description of creation:

At once came forth whatever creeps the ground,
Insect or Worme; those wav'd thir limber fans
For wings, and smallest Lineaments exact
In all the Liveries dect of Summers pride
With spots of Gold and Purple, azure and green:
These as a line thir long dimension drew,
Streaking the ground with sinuous trace; (PL 7.475-481)

But this is the narrator's perspective in describing the insects created in all their summer finery, which does not denote that Paradise has a summer season. Perhaps because there is no excessive summer heat, whereas both spring and autumn are temperate -- and also fit the astronomical conditions in which celestial equator and ecliptic coincide, such that day and night are always equal, precisely as upon the equinox. As previously noted, therefore, the true seasons with their changes came only after the fall, and the description of summer and winter fits this observation since the solstices are possible only when the celestial equator and the ecliptic no longer coincide:

While the Creator calling forth by name
His mightie Angels gave them several charge,
As sorted best with present things. The Sun
Had first his precept so to move, so shine,
As might affect the Earth with cold and heat
Scarce tollerable, and from the North to call
Decrepit Winter, from the South to bring
Solstitial summers heat. To the blanc Moone
Her office they prescrib'd, to th' other five
Thir planetarie motions and aspects
In Sextile, Square, and Trine, and Opposite,
Of noxious efficacie, and when to joyne
In Synod unbenigne, and taught the fixt
Thir influence malignant when to showre,
Which of them rising with the Sun, or falling,
Should prove tempestuous: To the Winds they set
Thir corners, when with bluster to confound
Sea, Aire, and Shoar, the Thunder when to rowle
With terror through the dark Aereal Hall.
Some say he bid his Angels turne ascanse
The Poles of Earth twice ten degrees and more
From the Suns Axle; they with labour push'd
Oblique the Centric Globe: Som say the Sun
Was bid turn Reines from th' Equinoctial Rode
Like distant breadth to Taurus with the Seav'n
Atlantick Sisters, and the Spartan Twins
Up to the Tropic Crab; thence down amaine
By Leo and the Virgin and the Scales,
As deep as Capricorne, to bring in change
Of Seasons to each Clime; else had the Spring
Perpetual smil'd on Earth with vernant Flours,
Equal in Days and Nights, except to those
Beyond the Polar Circles; to them Day
Had unbenighted shon, while the low Sun
To recompence his distance, in thir sight
Had rounded still th' Horizon, and not known
Or East or West, which had forbid the Snow
From cold Estotiland, and South as farr
Beneath Magellan. (PL 10.649-687)

[Thomas H. Luxon, ed. The Milton Reading Room, January 2009]

Without this turning, springtime would have remained perpetually (along with 'autumn', of course). Unlike Korea's "four distinct seasons," Paradise had only two, and these were indistinct.

Next, I'll probably need to look into the meaning of "season" in Milton's time, and perhaps thoughts on the seasons in Paradise by poets, scholars, and theologians before Milton.