It never gets really cold in Tanzania so lightweight clothing, preferably cotton or linen, is recommended. While on a game viewing safari, avoid brightly coloured clothing, stick to whites, beiges, khakis and browns. There may be long days sitting in safari vehicles, so it is advisable to wear light comfortable clothing such as short sleeved shirts and cotton/linen trousers or shorts. Denim will become too hot and extremely uncomfortable. Walking shoes and socks will be required.
The evenings will be chilly, so long sleeved shirts and trousers should be worn. A sweater may be needed. These will also prevent you being bitten by insects. A hat should be worn at all times outside. The sun may sometimes not feel hot, but it can still easily burn, especially if it is cloudy and overcast.
If visiting Zanzibar or any coastal town don't forget to take a swimsuit, as it is invariably warm. Ladies are recommended to take cotton skirts, blouses and dresses. Sandals are a must for this environment! On the beaches and within the confines of hotels, normal swimwear is acceptable but nudity is not.