Throughout Baldur's Gate 3, the party has had to camp outside in whatever conditions they find: seaside cliffs, Underdark caverns, shadow-cursed wastelands, abandoned farms, and so on. The game has no hard limit on the number of long rests the party can perform, but players must spend 40 Camp Supplies for each one.
Baldur's Gate 3: How to Get a Room in Elfsong Tavern
Players who reach Baldur's Gate won't have to camp outside once they get a room in Elfsong Tavern.