El Niño and the Fire Corridor

This is a new monthly column with a narrow job: take the official ENSO forecast, the one NOAA’s Climate Prediction Center and Columbia’s IRI issue every month, and say plainly what it means for fire and water in the 11-state corridor. Plenty of excellent writing explains what El Niño is; far less connects each month’s numbers to the landscapes that burn. That connection is the whole purpose of this column, and we will grade our own read of it, month by month, on the Scorecard.

Where the Pacific Stands

El Niño is established. The weekly Niño 3.4 index reached +1.7°C in June, already a strong event by the conventional +1.5°C threshold, and the July CPC/IRI update holds El Niño probabilities at effectively 100% through the Northern Hemisphere fall. The forecast’s most consequential detail: roughly half of the models indicate a very strong (“super”) event, ≥+2.0°C, at the autumn peak. Only three events in the modern record have reached that tier: 1982–83, 1997–98, and 2015–16. The atmosphere is coupled and the subsurface heat is there; this is not a borderline forecast.

What El Niño Actually Does to Fire, and What It Doesn’t

Honesty first: ENSO does not ignite fires, and its fire fingerprint is seasonal and regional, not uniform. The best-documented pathway runs through winter. In El Niño winters the storm track shifts south: the Pacific Northwest and Northern Rockies trend warmer and drier, while the Southwest trends wetter. For the northern corridor that means thinner snowpack, earlier melt-out, and a longer window in which fuels are dry enough to carry fire the following summer, the same snowpack-to-fire chain (Westerling et al. 2006) that this site’s homepage visualizationstrack all season. For the Southwest it can mean the opposite problem on a one-year delay: a wet winter grows a heavy crop of grass and fine fuels that cures into the next season’s fire load.

The summer signal is blunter: a strong El Niño adds heat to a planet already warming, and heat drives vapor pressure deficit, the atmosphere’s pull on moisture in soils and vegetation, which correlates with western burned area at r = 0.70 across the last four decades (Abatzoglou & Williams 2016; our own 41-year VPD panel). 2015–16, the last super event, brackets the danger: the 2015 season burned 10.1 million acres nationally, the largest total in the modern record at the time, with the Northwest at its center. That was the corridor’s worst season in decades, until this one.

The Uncomfortable Part: This Season Didn’t Need El Niño

The 2026 season was primed before the Pacific finished flipping. The snowpack collapse, 1,012 of 1,570 SNOTEL stations at all-time April 1 lows, eight states at record lows, all eleven at zero median SWE by late May, happened while the ocean was still exiting La Niña. The driest January–March on record for the continental US did too. El Niño is best understood as an amplifier arriving mid-disaster: it did not cause the 3.5 million acres now burning across the corridor, but its heat is in the summer that is burning them, and its peak is still ahead.

What to Watch Next

The autumn peak. Whether the event tops +2.0°C matters most for what comes after this fire season. A super El Niño winter loads the dice toward another warm, snow-poor winter in the Northwest, which would make 2027 the second consecutive season to start from a snowpack deficit, and snowpack deficits compound in reservoirs that are already at 23% (Powell) and 30% (Mead). The Southwest flip side. If the canonical wet El Niño winter materializes in Arizona and New Mexico, expect short-term drought relief there, followed by a heavy fine-fuel crop, a 2027 grass-fire setup we will flag now rather than in hindsight. Fall fire weather.The season doesn’t end at the equinox; offshore-wind season in California overlaps the El Niño ramp, and fuels there are at record dryness.

Those are checkable statements. When the CPC/IRI August update lands, this column updates with it, and where last month’s read was wrong, it will say so, in the text, not in a quiet edit.