Are inter-island flights as cold as the flights between the mainland and HI? I'm trying to decide if I need to keep my cold flight comfort items out and ready, or if they can safely go into my checked bag.
Inter-island flights in Hawaii are typically much shorter and less chilly than long-haul flights from the mainland to Hawaii. The flight times range from about 30 minutes to 1.5 hours, and the planes are usually smaller, such as regional jets or propeller planes, which do not have the same level of air conditioning as larger aircraft. However, most inter-island flights are still air-conditioned, so it’s not unusual for it to be a bit cooler than outside. But it's generally not as cold as the long flights between the mainland and Hawaii.
That said, you may still want to keep a light jacket or sweater handy, especially if you tend to get cold easily. The flight cabin can sometimes be chilly, but it’s usually not freezing like longer flights. If you prefer extra comfort, you could certainly bring a light layer in your carry-on, but it's likely safe to pack any heavier cold weather items in your checked bag.
In general, it’s not necessary to prepare for the extreme cold, but having a light, comfortable layer for the flight is a good idea, especially if you tend to be sensitive to air conditioning.