Den 1. maj mødes vi i parken, hvis vejret er godt nok til en lang tur.

You would normally read 1. as første, so Den 1. maj is said as den første maj.

The word den is a common way to introduce a specific date, roughly like on the 1st of May in English. In other contexts, Danish can also leave it out, especially after the verb: Vi mødes 1. maj is also possible.

In Danish, names of months and days are normally not capitalized. So you write maj, juni, mandag, tirsdag, etc.

That is different from English, where May and Monday must be capitalized.

This is because Danish main clauses follow the verb-second rule.

The first element in the sentence is Den 1. maj, so the finite verb must come next:

• Den 1. maj = first element
• mødes = second element
• vi = subject after the verb

So Den 1. maj mødes vi i parken is correct.

You could also say:

• Vi mødes i parken den 1. maj

That is also correct, but now vi is the first element, so the verb stays right after it.

Mødes is the natural form when people meet each other or meet up.

So:

• Vi mødes i parken = We’re meeting in the park / We’ll meet up in the park

By contrast, møder is usually used when someone meets someone or something:

• Vi møder ham i parken = We meet him in the park

So in your sentence, mødes is the right choice because the meaning is reciprocal: we meet each other.

Vejret means the weather, and that is the normal way to talk about the weather in a specific situation.

So:

• vejret er godt = the weather is good

The bare form vejr is more general or indefinite:

• godt vejr = good weather
• dårligt vejr = bad weather

In this sentence, you are talking about the weather on that particular day, so vejret is the natural choice.

Here godt nok means good enough.

So:

• vejret er godt nok til en lang tur = the weather is good enough for a long walk

A useful detail:

• godt is the neuter form of god
• vejr is a neuter noun, so the adjective becomes godt

Also, be careful: godt nok can mean something else in other contexts, such as indeed or actually. But in this sentence, it clearly means good enough.

Danish often uses nok til for the idea of enough for something.

So the pattern is:

• god nok til noget
• godt nok til noget
• stor nok til noget

Examples:

• Han er gammel nok til at køre bil = He is old enough to drive
• Det er varmt nok til en svømmetur = It is warm enough for a swim

So godt nok til en lang tur is the normal Danish structure for good enough for a long walk.

Hvis means if and introduces a subordinate clause:

• hvis vejret er godt nok til en lang tur = if the weather is good enough for a long walk

After hvis, Danish uses normal subordinate-clause word order, so you get:

• vejret er = the weather is

There is no inversion here. That is why you do not say hvis er vejret...

The comma marks the start of the subordinate clause introduced by hvis.

So the sentence is divided like this:

• main clause: Den 1. maj mødes vi i parken
• subordinate clause: hvis vejret er godt nok til en lang tur

Many Danish writers use a comma before subordinate clauses like this. In modern Danish, whether that comma appears can depend on the comma style being used, so you may also see the sentence without it. But the comma here is very common and completely natural.