Si tempestas bona manet, messis cras incipiet et omnes in agro laborabunt.

Si means if. It introduces a condition.

So Si tempestas bona manet is the if-clause: it gives the condition. Then messis cras incipiet et omnes in agro laborabunt is the main clause: it tells what will happen if that condition is true.

This is a straightforward real/open condition: the speaker is talking about a genuine possibility.

Latin does not have articles like English the and a/an.

So:

• tempestas can mean weather, the weather, or sometimes a storm
• messis can mean harvest or the harvest
• agro can mean a field or the field

You decide from the context what sounds best in English.

Bona is an adjective meaning good. It describes tempestas.

In Latin, adjectives must agree with the nouns they describe in:

• gender
• number
• case

Here:

• tempestas is feminine
• singular
• nominative (because it is the subject of manet)

So the adjective must also be feminine singular nominative: bona.

Yes. Latin word order is much more flexible than English word order.

Both tempestas bona and bona tempestas can mean good weather. The endings show which words belong together, so Latin does not rely as heavily on word order.

That said, different word orders can create slightly different emphasis or sound more natural in certain contexts.

Manet comes from maneo, which means remain, stay, or continue.

So tempestas bona manet is not just the weather is good. It has the idea that the good weather continues or holds.

Grammatically, manet is:

• 3rd person singular
• present tense
• active
• indicative

So literally it means it remains or it stays.

Because messis is a 3rd-declension noun.

English speakers often expect a word ending in -s to be plural, but in Latin that is not true. Here messis is singular, and it means harvest.

In this sentence, messis is the subject of incipiet, so it is nominative singular.

There are two main clues:

1. Messis is in the nominative form, which is the normal case for the subject.
2. Incipiet is 3rd person singular, so it matches a singular subject.

So messis incipiet means the harvest will begin.

They are both future tense, but they come from verbs in different conjugations.

• incipio belongs to the 3rd-io type, whose future looks like:
  • incipiam, incipies, incipiet...
• laboro belongs to the 1st conjugation, whose future looks like:
  • laborabo, laborabis, laborabit... laborabunt

So:

• incipiet = he/she/it will begin
• laborabunt = they will work

Different conjugations often form the future differently.

Because Latin verb endings usually already tell you the subject.

In laborabunt, the ending -bunt shows:

• future
• 3rd person plural

So laborabunt already means they will work.

Latin can add a separate subject if needed, and here it does: omnes.

Omnes means all or everyone.

It comes from omnis, but here it is being used substantively—that means the adjective is standing on its own like a noun.

So instead of saying something like all the people, Latin simply says omnes.

In this sentence, omnes is the subject of laborabunt:

• omnes laborabunt = everyone / all will work

Because in can take different cases depending on the meaning.

• in + ablative = in/on a place, showing location
• in + accusative = into/onto a place, showing motion toward

Here the meaning is location: they will work in the field.

So Latin uses:

• in agro = in the field

If the idea were into the field, Latin would use:

• in agrum

Agro is ablative singular of ager, meaning field.

It is ablative because it follows in in the sense of location:

• in agro = in the field

So this is a good example of a preposition governing the ablative case.

Cras means tomorrow, and it is an adverb.

Latin adverbs can often move around more freely than in English. So cras could appear in different places without changing the basic meaning.

For example, Latin could also say:

• messis incipiet cras
• cras messis incipiet

The sentence you have places cras between messis and incipiet, which is perfectly normal. Latin word order is often chosen for emphasis, balance, or style rather than strict rules like in English.