When you come to Tanzania, which is located just south of equator, you will learn that the country has a generally comfortable tropical climate.
But when you want to travel the country and see different places you have to consider the different temperatures due to the altitude variations. The temperature along the coast and in the highlands can be significantly different.
The coast can be humid and warm, and the monsoon winds bring rain in two major periods. If you are coming in mid March to late May, it is very usual to experience the big rain in the long rainy season called Masaika. The short rain called Mvuli, falls in November/December.
The inland and highland:
The inland and highland climate is mostly determined of the altitude. If you go to the central plateau you will feel it is cooler, like the mountain areas in southwest and northeast. You can experience that the temperatures occasionally drop below 15ºC in June/July.
Dar es Salaam:
Average max/min temperature 32 ºC/19 ºC.
April is the month with most rain.
Average max/min temperature 33 ºC/22 ºC.
April/May is the rainy months.
Average max/min temperature 29 ºC/8 ºC.
April is definitely the month of heavy rain, while June/July is cold at night!