When Bali's rainy season actually starts, per BMKG
When is the rainy season in Bali?
Per the official Bali climatology station, the current wet season began between October and November across the island's 20 climate zones, with the peak split between January, 9 zones, and February, 11 zones. The island does not switch seasons on one date.
Ask when Bali's rainy season is and every page answers with the same folklore calendar, November to March, stated as if the island flipped a switch. Indonesia's meteorological agency runs a climatology station on Bali that publishes an actual seasonal bulletin, and reading it changes the shape of the answer.
What BMKG actually publishes
The Stasiun Klimatologi Bali divides the island into 20 climate zones and issues, ahead of each season, a prediction with four elements per zone: the onset, the comparison against the 1991-2020 normals, the rain character, and the peak. Seasons are defined statistically, in ten day units called dasarian against a 50 mm rainfall threshold, not by anyone's impression of the sky.
What the current bulletin says
For the present wet season, the station's summary reads:
Awal Musim Hujan 2025-2026 pada 20 Zona Musim (ZOM) di Bali, diprediksikan berkisar pada bulan Oktober dan November 2025. Apabila dibandingkan dengan rata-rata awal musim hujan periode 1991-2020, maka sebanyak 8 ZOM Maju (lebih cepat) dari rata-ratanya.
Onset spread across October and November, with 8 of the 20 zones starting earlier than their thirty year average, and the season's character predicted generally Normal. The peak lands in January for 9 zones and February for 11: the two months our month pages describe as the season's heart, now with the station's own arithmetic behind them.
Why this beats the folklore calendar
Two things the proverb version cannot tell you. First, the island enters the season zone by zone over two months, so the coast you are on matters: neighbouring zones can sit in different seasons for weeks. Second, the calendar moves with ENSO and the Indian Ocean Dipole, which is why the bulletin exists at all: this season ran early in nearly half the zones.
For what each month feels like on the ground, the month by month guide carries the practical version.
What we could not establish
- Zone by zone onset dates in a form worth reprinting: the bulletin's
- tables are keyed to zone codes that mean little without its maps. We
- cite the summary the station itself puts forward.
- This page tracks a seasonal bulletin, so its shelf life is one season
- by design. It is re-verified when the station issues the next one.
Also asked
- Does the whole island enter the wet season at once?
- No. BMKG divides Bali into 20 climate zones and predicts an onset per zone. In the current bulletin the onsets spread across October and November, which is why two travellers a month apart can honestly report different seasons.
- Which are the wettest months?
- The bulletin puts the season's peak in January for 9 of the 20 zones and February for the other 11. January and February together are the heart of the wet season, which matches what our month pages describe.
- Is the calendar the same every year?
- No, and that is the point of citing a bulletin rather than a proverb. This season, 8 of the 20 zones started earlier than their 1991-2020 average. ENSO and Indian Ocean conditions move the calendar year to year.
- How does BMKG define the start of a season?
- In ten day units called dasarian, against a 50 mm rainfall threshold, measured per zone against the 1991-2020 normals. It is a statistical definition, not a first cloudy day.
How we verified this
What changed
- First publication, from the Bali climatology station's own bulletin. This page tracks the current seasonal bulletin and is re-verified when the next one is issued