Pacific Decadal Oscillation
As of October, the Pacific Decadal Oscillation (PDO) is in a Cool phase, 9 years in, the deepest on a record back to 1854 - and past El Niños have rarely ended one.
PDO Now and Next
- Now · NOAA NCEI, to Oct 2026
- Cool PDO · 9 years in · the deepest on a record back to 1854Lowest yearRecordLowest monthRecordCurrent State
- Months ahead · NOAA, issued Oct
- El Niño until about Apr-Jun · El Niño warms the coast · the PDO stayed cool the next year after 5 of 6 El Niño winters in a Cool phaseWhat Follows
- Usually · phases since 1854
- 7 earlier Cool phases lasted 2 to 47 years · 5 lasted longer than this one so farPhases
What It Is - The leading pattern of North Pacific sea temperature north of 20°N, in Warm and Cool phases that last years to decades. In a Cool phase the water along North America runs cool around a warm central North Pacific. A Warm phase reverses it.
How It’s Measured - NOAA NCEI measures how closely each month’s North Pacific sea temperatures (ERSST v5) match the PDO’s shape, after taking out the global ocean’s average warming (Mantua et al. 1997). The site sets the phase from the 12-month mean, at ±0.5.
What Drives It - Mostly ENSO, held by the ocean. El Niño deepens the Aleutian Low, whose winds warm the coast and cool the centre, and La Niña does the reverse. The upper ocean keeps that pattern for a year or more, and slow ocean waves and the Kuroshio Extension off Japan add a memory of their own (Newman et al. 2016) - which is why a phase can last a decade.
What It Brings - A Cool PDO deepens La Niña’s effects and blunts El Niño’s - colder Alaska and western Canada, a drier south-western US, a wetter eastern Australia. A Warm PDO does the reverse. Its effects are strongest in winter.
On This Page - NOAA’s monthly index since 1854, today’s sea temperatures with real example weeks, what followed every El Niño and La Niña year, every phase on record, its partners and its strongest years.
Current State
The North Pacific’s slow sea temperature pattern - Warm or Cool phases that last years, tilting ENSO’s effects around the Pacific.
PDO State
since Nov 2017PDO −2.26 Oct 2026 · 12-month −1.58
Lowest year 2024 −2.59RecordLowest month Jul 2025 −4.21Record
Cool coast, warm centre - La Niña’s effects deepened, El Niño’s blunted
ENSO · Partner
LikelyPeak+2.0°CRONI Aug-OctEl Niño · Very Strong
El Niño · Very Strong
Warms the North Pacific r +0.53 · ENSO ↗
PNA · Partner
+1.509 NovPositive · 30-day +0.53
Positive · 30-day +0.53
Its winter weather pattern r +0.27 · PNA ↗
North Pacific
Reading the Map
- The PDO’s two poles, boxed - the central North Pacific and the North American coast, always opposite. In a cool phase the coast runs cool and the centre warm. A warm phase flips both. Each label gives its box against 1991-2020 on the map’s day.
- The Aleutian Low’s winds, anticlockwise. Deeper in a Warm phase, they blow mild air up the coast and cold air over the open ocean. Weaker in a Cool phase, the pattern turns round.
- What the phase usually brings on land, mostly in winter - Alaska, the south-western US and Japan.
- The pills swap the latest day for a real week of each phase: the warm ‘Blob’ winter of 2014, a Neutral February (2017) and the record Cool PDO of July 2025.
- Sea surface temperature against 1991-2020 (NOAA OISST, a recent day). The PDO index takes the global ocean’s warming out first and this map does not, so both poles can look warm - the coast is then the less warm of the two.
- Alerts since 12 Nov 2025 - 14 in its reach, none PDO-linked (not hazards the phase usually brings there).
Key Terms
- Pacific Decadal Oscillation
- - The leading pattern of North Pacific sea temperature north of 20°N, with phases that last years to decades.
- Cool PDO
- - Cool water along North America, warm in the centre. It deepens La Niña’s effects and blunts El Niño’s.
- Warm PDO
- - The reverse - warm along the coast. It deepens El Niño’s effects.
- ENSO
- - Much of the PDO is ENSO’s echo, held by the slower ocean (r +0.53 by year).
- The phase
- - Set by the 12-month mean: ±0.5 or beyond counts. A single month says little.
The PDO is NOAA NCEI’s index from ERSST v5, monthly since 1854 (Mantua et al. 1997). The phase is the 12-month mean: Warm at ≥ +0.5, Cool at ≤ −0.5. Phases are runs of the 12-month mean’s sign, with flips shorter than two years folded into the phase around them.
The map is NOAA OISST v2.1’s daily sea surface temperature against 1991-2020; the boxes are its 30-45°N, 160°E-150°W and 25-55°N, 135-120°W means. The examples are OISST on those days, with NCEI’s PDO for the month.
Alerts from GDACS (Orange and Red, the last 12 months), flagged PDO-linked when the hazard fits how the PDO’s phase (its 12‑month mean) usually moves the place in that season, on the site’s own measured links.
What It MeansWhat It Means - PDO Briefing
For the year ahead
The PDO is Cool, and it moves over years, not weeks. A Cool PDO usually brings colder winters and more mountain snow to Alaska and the Pacific North-West. The southern US and northern Mexico tend to be drier and warmer, with drought more likely. Eastern Australia tends to be wetter, with stronger La Niña rains. Japan tends to be warmer. These are odds, not forecasts.
The partners
ENSO is a Very Strong El Niño. In a Cool PDO, the PDO stayed cool the next year after 5 of 6 past El Niño winters. The PNA is the winter pattern the PDO moves with. Its link is loose, with the two on the same side in 16 of 29 strong PDO years.
How this compares
This is the deepest Cool phase on the record back to 1854. It is not the longest, as 5 of 7 earlier Cool phases lasted longer. One of them, 1998-2014, ran for 16 years.
What to watch
NOAA's monthly PDO value for November comes early in December. NOAA's next ENSO outlook is due 12 Nov. A turn needs the 12-month mean to cross zero and stay there.
Written by Claude from this page's own data, every figure checked against it · 9 Nov 2026
What Usually Follows
ENSO Winters and the PDO’s Next Year
The PDO through every El Niño year since 1950 and the year after, beside this year - and what followed each pairing.
This Year
A Very Strong El Niño, but a Cool PDO. This Cool phase already holds the records - the lowest month, −4.21 in July 2025 Record, and the lowest year, −2.59 in 2024 Record. At −2.26 in October, the PDO is lower than at this point in any El Niño year since 1950. In the 6 past El Niño winters that came in a Cool PDO, it stayed Cool the next year in 5, averaging −1.00.
What That Means - The two pull against each other - El Niño warms the coast a Cool PDO keeps cool - but past El Niños have rarely ended a Cool phase, so the likeliest path is a weaker Cool PDO through 2027, with El Niño’s usual effects around the Pacific blunted rather than deepened.
Usually - The phase the PDO is already in matters most: a Warm or Cool phase held the year after in 25 of 29 El Niño and La Niña winters since 1950. ENSO only tilts it - the year after an El Niño, the PDO rose in only 13 of 26. Much of the PDO is ENSO’s echo, kept by the slower ocean.
| PDO That Year | El Niño | La Niña |
|---|---|---|
| Warm | +0.41Stayed 4 of 6 | +0.18Stayed 2 of 3 |
| Cool | −1.00NowStayed 5 of 6 | −1.44Stayed 14 of 14 |
| Neutral | +0.02Rose 9 of 14 | −0.62Rose 1 of 6 |
Each cell gives the PDO’s mean the year after, and how often a Warm or Cool phase held (from Neutral, how often the PDO rose). Hover a cell for its winters.
Warm and Cool Phases Since 1854
This Cool phase, since Nov 2017, is 9 years in with a mean of −1.47 - the deepest of the 8 Cool phases on record. 5 of the 7 earlier ones lasted longer.
A winter counts as El Niño or La Niña at a Nov-Jan RONI of ±0.5°C or beyond (NOAA CPC), labelled by its December. Its PDO phase is that calendar year’s mean (Warm at +0.5 or more, Cool at −0.5 or less), set beside the next year’s. The chart is NOAA NCEI’s monthly PDO (ERSST v5). Phases are runs of the 12-month mean’s sign since 1854, flips shorter than two years folded in. Newman et al. (2016) describe the PDO as largely ENSO’s effect, held and reddened by the slower ocean.
History
The PDO Since 1854
Every year since 1854, with the decades that leaned each way and the years remembered - and the month-by-month record.
Years Since 1854
30 / 68 / 74Warm, Cool, Neutral
Warm, Cool, Neutral
Beyond ±0.5, of 172 years
By Decade
+0.58 / −1.99The 1900s and the 2020s
The 1900s and the 2020s
6 of 10 years warm in the 1900s, 0 of 6 in the 2020s
Year to Year
r +0.52One year leans like the last
One year leans like the last
Year to year
PDO Years · Jan-Dec Mean, 1854-2025
Notable Years
Any Long-Term Change? - No clear trend: −0.01 a decade since 1854, within what chance gives (p 0.61). Warm years - 14 in 1854-1939, 16 in 1940-2025. Cool - 32, then 36.
NOAA NCEI derives the index from ERSST v5 sea surface temperatures north of 20°N in the Pacific (Mantua et al. 1997).
NOAA NCEI PDO index (ERSST v5).
The PDO's Partners
The PDO and Its Partners - Every Year Since 1950
The PDO each year beside ENSO and the opening winter’s PNA - where the bars line up with the shaded strong years, the partner moves with the PDO.
- ENSO (RONI)Clear Link
Drives It · Held for Years
Jan-Dec · r +0.53 · same way in 25 of 30
- PNAModerate Link
Partly Drives It · Through Its Winds
Dec-Feb, opening the year · r +0.27 · same way in 16 of 29
| Partner | SONDJFMAMJJA | vs PDO | In Strong Years | Link |
|---|---|---|---|---|
| PDO | The reference - the PDO’s yearly mean | |||
| ENSO (RONI)Drives It · Held for Years | r +0.53 | Same way in 25 of 30 | Clear Link | |
| PNAPartly Drives It · Through Its Winds | r +0.27 | Same way in 16 of 29 | Moderate Link | |
This Cool PDO Year So Far
- Lined Up
- None
- Against
- None
- Neutral
- ENSO +0.5PNA −0.4
Strongest past Cool PDO Years - partners lined up
Hatched bars - this year so far.
PDOJan-Dec
ENSO (RONI)Jan-Dec, °C
PNADec-Feb, opening the year
ENSO. Much of the PDO is ENSO’s echo, held for years by the ocean (Newman et al. 2016).
Same way in 25 of 30 strong PDO years · r +0.53ENSO Tracker ↗
PNA. The winter weather pattern whose winds over the Aleutian Low build the PDO’s sea temperatures (Newman et al. 2016).
Same way in 16 of 29 strong PDO years · r +0.27PNA Tracker ↗
The PDO is NOAA NCEI’s ERSST v5 index, each calendar year’s mean. ENSO is NOAA CPC’s RONI over the same year; the PNA is NOAA CPC’s index for the Dec-Feb winter that opens the year.
“vs PDO” is the correlation over every complete year since 1950. “In strong years” counts the years with the PDO beyond ±1.0 in which the partner was on the same side. A Clear Link is r 0.4 or more at p < 0.01, a Moderate Link r 0.25 or more at p < 0.05. Shaded years are those beyond ±1.0, the marked ones beyond ±1.5. Years in a row are not independent for a slow index like the PDO, so these p-values flatter the links.
The arrow under each partner is the direction the science gives, with its source in How Each Partner Works; the Link badge is what this record measures. The two can differ - a one-way influence can still be faint by the time it reaches the PDO, so its verb follows the badge (Drives It, Partly Drives It, Tilts It).
This season (2026) is provisional and not in the statistics - PDO Jan-Oct so far, ENSO Months so far.
Strongest Years
Strongest PDO Years - and What They Brought
Every year with the PDO beyond ±1.0 since 1950, strongest first, with Alaska, Northern Mexico, Japan and Eastern Australia that year.
Temperature against each place’s own trend, so decades compare fairly. Rain as a share of its 1961-1990 normal.
The PDO is NOAA NCEI’s ERSST v5 index, each calendar year’s mean. Temperatures are Copernicus ERA5 and rain GPCC for the same year - temperature against each place’s own straight-line trend since 1950, rain as a share of its 1961-1990 normal. Typical is the mean over every year of that kind in the list. Much of each year’s signal is ENSO’s, which the PDO largely follows.
PDO-Driven Places
PDO’s Pull by PlaceHow Much the PDO Drives Each Place
Each place’s strongest 3-month PDO link since 1950, beyond the same season’s ENSO and the world’s warming - across North America and East Asia.
Most PDO-Driven Places
Strongest link, either measure
One entry per country, its strongest part. Figures - the share of each season’s swing the PDO explains beyond the same season’s ENSO and the world’s warming. Tap a place for its figures, the arrow for the rest of the country.
Typical country’s share explained · strongest place
Figures are the share of a place’s year-to-year swing in that season that the PDO explains (r², 1950-present), the best of its twelve 3-month windows, after three things are taken out of both: the long-term trend, the same season’s ENSO, and the world’s warming (the global land-and-ocean temperature over the same months). A Strong or Moderate tier also needs a second window to agree.
The PDO is largely ENSO’s echo, held by the ocean (Newman et al. 2016). The ENSO step removes this season’s ENSO but not the PDO’s memory of last year’s, so some of ENSO’s reach is still in these figures. The PDO moves slowly, so every tier and phase count is judged on the effective sample size (Bretherton et al. 1999). Once ENSO and the warming are out, little memory is left, so it rarely moves a tier.
Ranked inside the PDO’s documented reach - Alaska, western Canada, the US West, South and Southeast, Hawaii, Mexico, Japan, the Koreas and China (Mantua et al. 1997); places elsewhere can still be found in the search. Southern Africa, eastern Australia and western South America are left out: the PDO works there by changing ENSO’s effect (Power et al. 1999), and beyond ENSO almost nothing is left. East Asia’s summer link leans on the record Cool PDO and record heat since 2021. A Warm or Cool PDO season is a 3-month mean of ±0.5 or beyond. Sources are NOAA NCEI’s monthly PDO, Copernicus ERA5 temperature and GPCC rainfall by country and US state.
Contains modified Copernicus Climate Change Service information 2026.
Regional Impacts
Where Does the PDO Bite Hardest?
What each PDO phase usually brings around the Pacific - strongest in winter, and mostly by deepening or blunting ENSO.
Warm PDO
Cool PDOToday
Alaska, western Canada, Pacific NW
Warmer
Warm coastal seas and a deeper Aleutian Low - milder winters, less snowpack.
Cooler
Cool coastal seas - colder winters and more mountain snow.
Southern US, northern Mexico
Wetter · cooler
An active southern storm track, as in El Niño winters.
Drier · warmer
Drought more likely - the south-west droughts of the 1950s and 2020s.
Eastern Australia
Drier
La Niña rains weaker - drought runs more common.
Wetter
La Niña rains stronger - floods more common (Power et al. 1999).
Japan, East Asia
Cooler
A deeper Aleutian Low draws colder air south in winter.
Warmer
A weaker Aleutian Low and warm seas off Japan.
North Pacific fisheries
Alaska salmon up
Warm years favour Alaskan salmon over Pacific NW runs.
Pacific NW salmon up
The original PDO finding (Mantua et al. 1997).
Tendencies over years, not forecasts.
From Mantua et al. (1997, BAMS), Newman et al. (2016, J. Climate) and Power et al. (1999, Climate Dynamics), checked against the site’s own measured links (Strongest PDO Years).
Explore
Where Next
- Coral Bleaching Tracker
Daily heat stress for 214 reef regions, bleaching alerts and the NOAA four-month outlook
- Indian Ocean Dipole
The Indian Ocean's own ENSO - the East Africa vs Indonesia and Australia rainfall seesaw
- NAO Tracker
North Atlantic Oscillation - a key driver of Europe's winds, storms and winter weather
- Global Climate Update
Whole-planet temperature, CO₂, sea ice and ENSO in one monthly update