The Tanzania Meteorological Authority (TMA) said on Thursday destructive heavy rains are expected to hit 16 regions from Thursday to Friday.
The rains, coupled with thunderstorms, will flood residential areas in valleys and damage farms, the TMA said.
"There will be disruption of transportation and some social services and businesses will come to a standstill," it said.
The 16 regions likely to be hit by heavy rains as Dar es Salaam, Coast, Kagera, Geita, Mwanza, Shinyanga, Simiyu, Mara, Tanga, Mbeya, Songwe, Rukwa, Iringa, Njombe, Ruvuma, and Zanzibar.
In May, heavy rains caused serious flooding in Dar es Salaam, resulting in the displacement of over 1,000 households and the destruction of more than 1,500 dwellings and important infrastructure.