El Niño winter 2026–27:
what past strong ones did.
How many of the 9 past strong El Niño winters were wetter than normal: Miami-Dade 8 of 9, Los Angeles 7 of 9, Harris 6 of 9, Chittenden 6 of 9, Denver 4 of 9. Details for each county are below.
This winter (December 2026 to February 2027): NOAA gives El Niño conditions a 100% chance (issued 8 October 2026); IRI gives 100% (issued 19 October 2026). That means the ONI (Oceanic Niño Index) in the tropical Pacific is expected at +0.5°C or higher; it is not a forecast of local weather. The NOAA discussion of 8 October 2026 says a strong-to-very strong El Niño is likely through January–March 2027, with a chance above 83%.
What strong El Niño winters did in five counties
- Los Angeles: wetter than normal in 7 of 9 strong El Niño winters; the median winter had 133% of normal rain.
- Denver: wetter than normal in 4 of 9 strong El Niño winters; the median winter had 96% of normal rain.
- Miami-Dade: wetter than normal in 8 of 9 strong El Niño winters; the median winter had 156% of normal rain.
- Harris: wetter than normal in 6 of 9 strong El Niño winters; the median winter had 109% of normal rain.
- Chittenden: wetter than normal in 6 of 9 strong El Niño winters; the median winter had 109% of normal rain.
The US pattern: NOAA says that during El Niño winters the southeastern U.S. is more likely to get more rain than average and northwestern North America is more likely to be warmer, but US impacts are less consistent than tropical ones.
Read the method, sources and limits.
What the ONI is
The Oceanic Niño Index (ONI) is the three-month average sea surface temperature anomaly in the Niño-3.4 region of the tropical Pacific, and NOAA calls El Niño present when it is +0.5°C or higher. NOAA also publishes seasonal El Niño temperature and precipitation patterns.
Past tendency is not a forecast. Averages hide local differences. Nothing here is a property-level finding.
How the El Niño county results are built.
Strong winters
A winter runs from December to February. It counts as strong when the largest of the NDJ, DJF and JFM ONI values around it is at least 1.5°C. NOAA’s historical record identifies these winters from 1951–52 to 2024–25: 1957–58 (1.7), 1965–66 (1.6), 1972–73 (1.8), 1982–83 (2.1), 1991–92 (1.5), 1997–98 (2.4), 2009–10 (1.5), 2015–16 (2.6), 2023–24 (2.0). Values are rounded to 0.1°C. NOAA now uses the Relative ONI (RONI) for official monitoring. We use ONI for history because it is the long published record. The 2026–27 odds come from NOAA’s RONI-based consensus and IRI. They describe El Niño conditions in the tropical Pacific, not local weather.
Rain, heavy-rain days and temperature
NOAA county climate records provide county area averages of daily precipitation and daily mean temperature. Winter rain is the December–February total. Normal is the average of the 30 winters from 1990–91 to 2019–20. Rain is shown as a percentage of normal. The lede gives the number of wetter strong winters and the median percentage; the mean stays in the values file. Heavy-rain days have at least 25.4 mm (1 inch) of county-average rain. Their normal uses the same 30 winters. County averages smooth local downpours, so counts are lower than at a single gauge.
Winter temperature is the mean of daily values. We fit a straight line by least squares to all 74 winter means from 1951–52 to 2024–25 in each county. Each strong winter is compared with that line. Celsius departures are multiplied by 9/5 for °F. This accounts for a long-term trend; it does not establish an El Niño cause. Daily records start in January 1951, making 1951–52 the first complete winter. An alternative NOAA county series was unavailable on 22 October 2026.
Flood claims
FEMA supplies National Flood Insurance Program claims, grouped by county and date of loss from December to February. Records cover 1978 onward. Counts include every claim record, paid or not, and only insured losses. They do not measure damage size. Each strong winter is ranked among all 47 winters from 1978–79 to 2024–25. Rank 1 means most claims; equal counts share a rank, and zero claims show no rank. We also give the median winter. Insured exposure grew, so counts are not comparable across decades. We did not calculate claims per policy because a clean county-by-year policy count was unavailable.
Limits
- Past tendency is not a forecast. Nine winters are a small sample.
- County averages hide local differences, including mountains and coasts.
- El Niño is one of several influences on a winter.
- These are county results, not property-level findings.
Sources
NOAA supplies county climate records and Pacific climate assessments. IRI supplies a separate Pacific climate assessment. FEMA supplies flood insurance claims and emergency guidance. The insurance wording check draws on Pillsbury Winthrop, 2013.
Download the county values.
Questions about El Niño and US counties
What is El Niño?
El Niño is a warming of surface waters in the east-central tropical Pacific. NOAA says it is present when the ONI is +0.5°C or higher. During El Niño winters, the southeastern U.S. is more likely to get more rain than average, and northwestern North America is more likely to be warmer than average. Source: NOAA.
Which winters count as strong here?
A winter counts as strong when the ONI peak around it is at least 1.5°C: 1957–58, 1965–66, 1972–73, 1982–83, 1991–92, 1997–98, 2009–10, 2015–16, 2023–24. Of these, 6 fall inside the flood claims data, which start in 1978. Source: NOAA.
Does a strong El Niño mean a wet winter for my county?
Not always. In our five counties, between 4 and 8 of 9 strong El Niño winters were wetter than normal. See the county findings above.
Is the 2026–27 El Niño strong?
NOAA says a strong-to-very strong El Niño is likely through January–March 2027, with a chance above 83%. Assessment issued 8 October 2026.
What should a property team do now?
Check flood deductibles and sub-limits, buy flood cover early because a National Flood Insurance Program policy typically takes 30 days to go into effect, raise critical equipment above the flood level, and ask tenants to move valuables up. Sources: Pillsbury Winthrop; FEMA.