Why do I lose my voice twice a year?

Every year in March and August I lose my voice. One morning I’ll wake up and it’ll just be gone. After a couple days without speech, it will return to normal. This has been going on for five or six years. It hasn’t really been too much up an issue up until now – I’m running front of house for a chamber music festival here in town and now am seemingly incapable of directing volunteers and talking to patrons without sounding hideous.

Why does this happen?? And more importantly, how can I fix it?

(PS: Already drinking my tea with honey.)