Will I overheat in an expedition parka on warmer days?

Yes, almost certainly. Expedition parkas are designed for extreme cold and will cause overheating above approximately -10°C, even with pit zips open and minimal layering underneath. If you ride in a wide temperature range, consider a detachable powder skirt model and be prepared to open all vents and wear only a thin base layer underneath on warmer days. For riders who experience significant temperature variation, a shell-plus-midlayer system is almost always more practical than an expedition parka, as you can adjust the mid-layer to match conditions while the shell provides consistent weather protection.