This is the 2919th most frequent French word.
extérieures
External; outer; outside.
In this sentence, 'extérieures' is used as an adjective to describe 'activités', indicating they happen outside or outdoors.
Les activités extérieures sont meilleures pendant l'été.
Outdoor activities are better during the summer.
Here, 'extérieurs' modifies 'murs', specifying they are the walls located on the outside part of a building.
La peinture des murs extérieurs nécessite un entretien régulier.
The paint on the exterior walls requires regular maintenance.
'Extérieures' is used here to qualify 'influences', meaning influences coming from outside or external sources.