All of the inhabited parts of Antarca are underneath domes and roofs so it never actually rains, of course. But at some point someone decided either that rain is too important to people’s psychological well-being to skip, or that it’s the most efficient way to clean the city, or that it’s necessary for watering the greenery, or maybe all of those. So it “rains,” periodically, on a set schedule, in different parts of the city at different times, via pipes and sprinklers. They had to build all that in for fire suppression anyways, so why not give it a secondary function?

↓ Transcript
Panel 1: The outside of Maida's block of flats. It's dark and the only lights are from windows, streetlights, and balconies. It looks like it's raining heavily.
Panel 2: Maida comes in the door quietly and closes it behind her. She's soaking wet.
Panel 3: Maida's aunt gets up from the kitchen table. Ujana: (in Swahili) "Maida! Where have you been!?" Maida: "Oh. Hi, Anti."
Panel 4: Ujana: "You left school early and then the map said you were clear on the other side of Antarca!" Maida takes off her hijab.
Panel 5: Ujana: "There's an exclusion order in my inbox. Did you hit someone!?"
Panel 6: Maida, not looking her aunt in the eyes: "Y-yes? Um... It's a long story."