As Tanzania prepares for the 2026 Vuli season, the Tanzania Meteorological Authority (TMA) has forecasted above-average to average rainfall across much of the northern coastal belt, northeastern highlands, Lake Victoria basin, and northern Kigoma. The rains are expected to begin around the fourth week of September and first week of October in the Lake Victoria basin before spreading gradually to other areas. This forecast is significant as the country prepares for a strong El Niño, which is expected to influence the rainfall season.
According to TMA weather expert Alfred Kondowe, 'above-average rainfall' does not mean one fixed amount of rainfall for the entire country. Instead, it means that the rainfall expected in a particular place is likely to exceed the amount that normally occurs there during a particular period. This is based on historical rainfall records, location, season, and the probability of different rainfall outcomes. The TMA uses a 30-year reference period, from 1991 to 2020, to calculate the climate normal used for comparison.
Meteorologists establish what is considered normal by comparing current expectations with long-term historical records. For example, if Dar es Salaam normally receives a certain amount of rainfall during October, November, and December, a seasonal total expected to exceed that historical level would be classified as above average. The important point is that the average is not the same everywhere, as Tanzania has different climatic zones. A rainfall amount considered high in one region may be normal in another.
The TMA's seasonal forecast is probabilistic and is designed to describe an expected tendency rather than provide an exact rainfall total months in advance. This means that the actual amount can only be established after the season has occurred and rainfall observations have been collected and analysed. Kondowe stressed that 'above average' does not mean rain every day, but rather that the seasonal total could be pushed upward by rainfall during particular periods.
The 2026 forecast illustrates this point, with the Vuli season expected to receive more rainfall, particularly in November and December. This means that the seasonal total could be pushed upward by rainfall during particular periods rather than continuous rain throughout the season. This distinction is important for farmers, traders, construction companies, transport operators, and households, as it helps them prepare for the expected conditions.
TMA weather analyst Ramadhani Omary emphasised that El Niño is not rain, but rather a weather system that refers to an increase in sea-surface temperatures in the central and eastern tropical Pacific Ocean. When this warming persists, it can alter atmospheric circulation and weather patterns in different parts of the world. For Tanzania, El Niño is expected to increase rainfall, particularly towards the end of the year and the beginning of the following year.
The impacts of El Niño cannot be understood simply by looking at the strength of the Pacific warming, as other climate systems, including conditions in the Indian Ocean, can modify its effects. Understanding these nuances is crucial for effective preparation and response to the 2026 Vuli season. The TMA's forecast and explanations aim to help the public prepare for the expected conditions and make informed decisions.
Key points
- The Tanzania Meteorological Authority forecasts above-average rainfall for the 2026 Vuli season, influenced by a strong El Niño.
- 'Above-average rainfall' refers to rainfall expected to exceed historical levels in a particular location, not a fixed amount for the entire country.
- El Niño is a weather system that can alter atmospheric circulation and weather patterns, but it is not rain itself.
