I have allergies to cats, pollen, and dust. right now we are experiencing a hurricane also.

Headache: If this sudden onset headache is very severe and unlike any you've ever experienced, it warrants a trip to the emergency room where examination including a brain ct scan can be promptly obtained. However you describe it as moderate and the accompanying description suggests sinus congestion or inflammation as a cause. Allergies may have predisposed you to sinusitis. Treat congestion. See MD as need