Wear light clothing, with layers if you run cool. The aircraft does not have air conditioning, just fresh air vents. The temperature at our flight altitude is about the same as on the ground, so dress comfortably for the day. Without much airflow, if we have full sun it can get quite warm inside, so it’s more likely to be hot than cool.
We recommend just bringing a phone/camera, a water bottle (we like to reduce plastics), and wearing closed-toe shoes and sunglasses (even if it doesn’t look sunny).
We suggest that you only bring with you what you need for the flight, as the plane is quite cozy, though if you have extra bags they can be locked in our office or a locker while we’re in the air.