Farmers, pray for summers with lots of rain,
And winters with lots of sun.

[Humida solstitia atque hiemes orate serenas,
agricolae.]

Virgil (70-19 BC) Roman poet [b. Publius Vergilius Maro; also Vergil]

Georgics [Georgica], Book 1, l. 100ff (1.100) (29 BC) [tr. Ferry (2015)]
    (Source)

(Source (Latin)). Alternate translations:

Swaines pray for winters faire, and summers wet.
[tr. Ogilby (1649)]

Ye Swains, invoke the Pow'rs who rule the Sky,
For a moist Summer, and a Winter dry.
[tr. Dryden (1709), ll. 146-147]

Ye husbandmen! intreat the gods by pray'r
For wat'ry solstices, and winters fair.
[tr. Nevile (1767)]

Swains! pray for wintry dust, and summer rain.
[tr. Sotheby (1800)]

Pray, ye swains, for moist summers and serene winters.
[tr. Davidson (1854)]

For winters dry, and showery summers, pray.
[tr. Blackmore (1871), l. 116]

Pray for showery summers and dry winters, husbandmen.
[tr. Wilkins (1873)]

Pray for wet summers and for winters fine,
Ye husbandmen.
[tr. Rhoades (1881)]

Now pay thy vows: be this the ploughman’s prayer:
Bright be the winter day, and moist the summer air.
[tr. King (1882), ll. 99-100]

Pray, ye swains, for moist summers and serene winters.
[tr. Bryce (1897)]

Pray for dripping midsummers and clear winters, O husbandmen.
[tr. Mackail (1899)]

Pray for wet summers and for winters fine,
Ye husbandmen.
[tr. Greenough (1900)]

For drizzling summers and sunny winters, husbandmen, pray.
[tr. Way (1912)]

For summers moist and windless winters fair
Pray heaven, ye farmer-folk.
[tr. Williams (1915)]

For moist summers and sunny winters, pray, farmers!
[tr. Fairclough (Loeb) (1916)]

Wet midsummers and fair winters are what the farmer
Should ask for.
[tr. Day-Lewis (1940)]

Pray for wet midsummers, farmer friends,
And clear, cold winter skies.
[tr. Bovie (1956)]

Wet skies in midsummer and clear in winter
Farmers should pray for.
[tr. Wilkinson (1982)]

Farmers, pray for moist summers and mild winters.
[tr. Kline (2001)]

Farmers pray for wet summers and winters with clear blue skies.
[tr. Lembke (2004)]

The countryman should pray for wet summers and mild winters.
[tr. Fallon (2006)]

For humid summers and winters mild, pray, O farmers.
[tr. Johnson (2009)]

O farmers, pray that your summers be wet and your winters clear.
[Bartlett's]