"Msimu wa vuli"
Indeed, check this out, according to vf-tropi.com. Tanzania's Masika and Vuli Rains Defined
Tanzania has two major agroclimatic areas - the unimodal and the bimodal rainfall areas. The bimodal area has a short-rains minor cropping season, known as vuli, with planting around October/November and harvesting in late January/February; and a main, long-rains season, called masika, following immediately the vuli season, with planting in late February/March and harvesting in July/August. The bimodal areas extend over the northern and north-eastern regions, including Kilimanjaro, Arusha, Moshi, Tanga, as well as Kigoma, Kagera, Mwanza, Mara and parts of Morogoro, Mbeya, Dar es Salaam and Coast. Elsewhere in the country, i.e. the central and southern regions, rainfall is unimodal, with planting starting around November and harvesting taking place from May to July. In some regions, the unimodal or "seasonal rains" are also referred to as masika.
It's also not how they would commonly translate it in EA. Should be "season of short rains"
Short rains yes, but autumn is a temperate term...and Fall north American, it should not be used as the english equivalent?
This was very confusing, coming across it the first time. It should be a phrase rather than three separate words.
As the others wrote here, try the more accurate answer "season of short rains" and report it if this answer still isn't accepted.