Seriously. Wear one on your head. most tornado injuries are blunt force trauma.

Any PPE should help prevent injury, so don't limit to only your head.

However i think choosing the right helmet can be a hard decision. There is no tornado certification for a helmet. Hard shell, with primarily protection from above, or foam type with side and above protection? With or without chinstrap? What kind of chinstrap (brake away anti strangle one or not)? Does it need to compatible with visors, ear protection, headlights, etc?

I think the kids would wear something like a skate board helmet..

Any helmet is better than no helmet and an unprotected cranium. Even a construction hardhat. Right now I could choose between a climbing helmet (Petzl), a bicycling helmet, and a construction grade hard hat, courtesy of CERT training. Typical retail costs range from eight dollars (hard hat) to around 100 bucks (climbing helmet). The climbing helmet offers the best protection and will most likely remain on the head after first impact.

The Cert hard hat, my most recent acquisition, came without a chin strap, seriously diminishing its capability. I was glad to find one that works. Now it is actually useful around modest hazards.

Well most hardshell climbing helmets do not really protect from side impacts. It's not a part of the certification for climbing helmets. The chinstrap does keep the helmet on, but having the helmet knocked off you head also reduces the impact on you head and prevents you from being strangled...

The one I am most likely to wear is my bicycling helmet because the best helmet to wear in a tornado is the helmet you have with you. It is a Kong Scarab (Italian) with European certification for mountaineering, canoeing and white water sports, equestrian activities, and cycling and 'users of skateboards and roller skates." Doesn't say a thing about tornadoes or windstorms - darn those careless Europeans! I really like it - it is comfortable, reasonably protective, and it stays on my head, thanks to an excellently designed chinstrap.

I would think, in addition to a helmet, it would be smart to get your body, especially the cranium, into a protected location (behind the sofa or next to the bed) and provide additional shielding with one's arms.....

At $10 seems like a deal

With the addition of a wind mitigation device and hearing protection, should serve well for tornado applications.

I use an older style PASGT Kevlar helmet and suppliment it with one of those vietnam era flak jackets (USMC m1955(?)), mostly because I just had them laying around.

You can find the helmets for ~$50 and surplus flak jackets run about the same when you can find them. I know there are some german surplus flak jackets floating around the internet too. Obviously you'd need to check your local laws on the legality of owning body armor in your area.

A helmet without a chinstrap in >100mph wind is going to be gone in a split second.

While cowering in the basement in one of the few times we've done so because of imminent tornado threats the fact that my personal hardhats were within reach meant they went onto our heads while we waited.

Couldn't hurt and might help. Be stupid to get whacked in the head by collapsing house when a hardhat is right there doing nothing but protecting the shelf it's on.