Singapore — Seasonal Weather Overview

Nov – Dec – Jan 2025–2026 (drivers: monsoon, winds, ITCZ, MJO, IOD, weak La Niña)

Executive summary

Expect an inter-monsoon pattern with frequent afternoon & evening thundery showers in November, transitioning to a strengthening Northeast Monsoon in late-November/early-December. December and January will bring more sustained showers, cooler spells during monsoon surges, and occasional windy conditions. Background climate drivers (weak La Niña, negative IOD tendency, and possible MJO pulses) increase the chance of above-average rainfall during some periods.

Key drivers (what’s causing this)

Monsoon / wind change — Inter-monsoon in November with light variable winds, moving to a prevailing north-east flow by late Nov/Dec (Northeast Monsoon).
Maritime/ITCZ shift — Seasonal cooling and southward shift of convective ITCZ across the Maritime Continent usually modifies moisture distribution and promotes more organized coastal rainfall during the NE monsoon phase. :contentReference[oaicite:3]{index=3}
MJO pulses — Model outlooks show intermittent MJO activity reaching the Maritime Continent around the Nov–Dec window; when the MJO is active it commonly enhances convection and increases rainy/thundery episodes.
Indian Ocean Dipole (IOD) — Recent indications of a negative/active IOD (warmer eastern Indian Ocean) bolster moisture supply to the eastern Indian Ocean / Maritime Continent region, supporting wetter anomalies at times.
Weak La Niña — ENSO guidance favors a weak La Niña persisting into boreal winter, which tends to favour enhanced convection in parts of the Maritime Continent and can modulate monsoon surge frequency/intensity.

Monthly outlook (high-level)

November 2025

Predominantly inter-monsoon conditions early in the month with frequent hot afternoons and thundery showers. By late November expect winds to gradually become more north-easterly as the Northeast Monsoon establishes — this increases coastal & offshore convective activity plus risk of squalls.

December 2025

Northeast Monsoon generally in place. Expect more sustained spells of showers and occasional monsoon surges that bring cooler, windier and wetter periods. Afternoon thunderstorms still possible during breaks in flow or where land-sea convergence is strong.

January 2026

Typically the wet phase of the NE monsoon — continued chance of heavy showers, localized flooding risk during intense cells, and episodic cooler temperatures (relative to Singapore norms) during strong surges. MJO or IOD-related pulses can produce above-normal rainfall during short spans.

Advice & practical guidance

Carry an umbrella; expect wet afternoons and rapid onset heavy showers.
Short-term flood risk in low-lying / poor drainage areas during intense convective bursts.
Marine interests: watch for squalls, gusty winds, and reduced visibility during heavy showers and surges.
Aviation & outdoor events: allow contingency for sudden changes, lightning and gusty winds.