How do I know if it is temporal arthritis?

Several... First see your doctor, since this is potentially a very serious condition. Most people have a temporal headache, but any blood vessel in the scalp or vein could be involved. A high CRP and ESR are the rule. Magneti resonance angiogram and biopsy are needed for definitive diagnosis. You should be followed by a rheumatology specialist, or at least seen inconsultation with one, if this is diagnosed!