Powerful rains have destroyed or damaged tens of thousands of houses, plus classrooms, medical centres, granaries and cattle herds.
Some 225,539 people have been affected and nearly 200 more injured, the figures showed.
The new toll is up from the latest update of 103 dead by early September.
The meteorological service has warned heavy rain will continue until the end of the month.
The floods have combined with regional droughts and jihadist insurgencies that have badly hit harvests.
Niger is going through a serious food crisis with health monitors warning more than 4.4 million people are facing “severe” food insecurity — a fifth of the population.
Severe floods in Niger after months of heavy downpours have killed 159 people, authorities said Monday, marking one of the deadliest rainy seasons in history for a normally arid state.
The landlocked Sahel state’s annual rainy season typically runs between June and August or September.
But in recent years, rainfall has become more intensive, accelerating the risk of deadly flooding in shantytowns.
Official figures shared with AFP show that so far this year, 121 people have died when their houses collapsed and another 38 have drowned.
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