This is a bug that everyone is getting really annoying about.
First thing, these events don't just happen one at a time, it's usually Storm + Headcrabs, or Storm + Combine. Rarely the Headcrab and Combine events happen without the aid of a Storm. These events are not rare at all, they happen TOO much. The Storms are the BIGGEST problem. They happen every single 10 minutes and last sometimes over 5 minutes and then RIGHT WHEN THEY'RE DONE, it happens again. It's become a nuisance. Everyone just wishes storms would happen once every 30 minutes and last at the longest 5 minutes.
Yes, you guys did really well making these events and they sure are fun at times(excluding the storm), but they still need to be refined.