I wouldn't advise it for two reasons. One, I don't think the ventilation in the ski helmets is nearly as good as those made specifically for biking. I haven't done a side-by-side comparison, but my biking helmet has many more and larger vents. Seems a no brainer that the bike helmet would be cooler in hot conditions. Two, I paid substantially more for my ski helmet than the bike helmets I have used over the years. I would rather prolong the life of my ski helmet by not using it for off season biking. Of course, this is not to say that there aren't expensive bike helmets but, whatever the reason, dollars go farther with bike helmets than ski helmets.