Electrum can be used as a cold wallet, however by default or the most common usage it's not. If you ran Electrum in a offline environment, it would be considered cold storage, but even then you have to handle the downloading of Electrum, and the transfer to a offline computer, very carefully.

Also, it could technically still be stolen or compromised. There's always a physical threat, and it entirely depends on how you've secured it. Plus, there's no such thing as absolute security, there's always going to be flaws whether that's through the user or the software itself. You can only reasonably secure something, since you aren't going to know all the flaws until they're discovered, and there's been many in the past.