Learn Spanish (Spain): En verano asamos sardinas en la playa. - In summer we grill sardines on the beach.

You have to look at the context. The phrase en verano (in summer) suggests a recurring habit or tradition, which points to the present tense. If the speaker meant a specific past event, they would usually say el verano pasado (last summer).

Why is it en verano instead of en el verano?

When using the preposition en to say something happens "in summer", "in winter", etc., Spanish usually drops the definite article. You only use the article if you are specifying a particular summer, like en el verano de 2023, or when the season is the subject of the sentence, like el verano es caluroso (summer is hot).

Why doesn't sardinas have the word las in front of it?

We omit the article here because we are talking about an unspecified quantity of sardines. Just like in English, when a plural noun is the direct object of a verb and refers to a general amount rather than specific ones, you don't use the definite article. If you said asamos las sardinas, it would mean "we grill the sardines" (specific ones we already bought).

The translation says "on the beach", so why use en instead of a specific word for "on"?

The Spanish preposition en does a lot of heavy lifting and covers the English words "in", "on", and "at". When talking about being physically present at a location like la playa (the beach), en is the correct and most natural choice.