Short thundery showers are expected on a few days over parts of the island between late morning and afternoon during the next two weeks.
But rainfall for the first half of October is forecast to be below average over parts of the island.
The weather is expected to be warm and less wet compared with last month.
The daily maximum temperature is forecast to be between 33 deg C and 34 deg C on most days, with highs of around 35 deg C on a few days, the Meteorological Service Singapore said on Friday.
Low-level winds from the south-east or south-west are forecast to persist and weaken around mid-month.
The weather at night may be warm and humid, with temperatures of around 28 deg C. This happens when the prevailing south-east and south winds bring warm and humid air from the sea over the land.
A low-pressure system over the northern South China Sea leading to the development of Sumatra squalls over the Strait of Malacca could also bring widespread thundery showers and gusty winds to Singapore between pre-dawn and morning on some days.
Last month, similar south-west monsoon conditions were seen over the region.
Thundery showers fell over parts of the island in the late morning and afternoon on most days due to strong daytime heating of land areas and convergence of winds over Singapore and the vicinity.
The highest daily total rainfall recorded last month was on Sept 2, with 123.6mm in Ang Mo Kio.
The highest daily maximum temperature of 34.8 deg C was logged in Sentosa on Sept 17, and the lowest daily minimum temperature of 22 deg C was recorded in Tengah on Sept 7.