2026 heat and temperature predictions: hottest year, heat domes, and climate records
Key highlights
- NASA GISS ranks 2024 the hottest year on record, 1.28°C above its 1951-1980 baseline, with 2025 and 2023 in a near tie for second inside the agency's own margin of error. NOAA, Copernicus, and Berkeley Earth measure against different baselines and can rank that order differently.
- NOAA's Climate Prediction Center placed the Pacific in an El Nino Advisory in its July 9, 2026 outlook, putting the chance of a very strong event by year end near 81 percent. That is a reversal from the cooler conditions forecasters expected at the start of the year, and the single biggest swing factor for where 2026 lands.
- The daily city-high markets each settle off one named weather station, LAX for Los Angeles or Central Park for New York, not a citywide average and not a forecast. The contract text names the station; the market title does not.
NASA's GISS analysis decides the hottest-year ranking, posting its annual figure in January against a 1951-1980 baseline. NOAA NCEI runs its own ranking off a 1901-2000 baseline the same week, and the two can order a close year differently. The daily city-high contracts each settle off the National Weather Service Daily Climatological Report for one named station, LAX for Los Angeles or Central Park for New York, first posted a few hours after midnight local time. The Arctic sea-ice contract settles off the NSIDC Sea Ice Index once the September minimum is called, usually mid-to-late month. The CO2 contract settles off NOAA's Mauna Loa monthly mean, posted after each calendar month closes.
The 2-degree warming contract measures the annual global mean against a pre-industrial 1850-1900 baseline, which sits about 0.2°C below the 1951-1980 baseline the hottest-year markets use, so the same year reads hotter on the warming contract than on the ranking one.
A record needs the back half of 2026 to run hotter than the front half, because the annual figure is a twelve-month average and the January to June anomalies are already published. An El Nino peaking in the October to December window falls inside that back half, which is why an ENSO outlook moves the hottest-year brackets more than any single hot month does. The number to watch is each monthly GISS anomaly, posted in the middle of the following month, against the 1.28°C pace 2024 set (NASA GISS).
Where the temperature record stands going into 2026.
The agencies publish their own rankings from overlapping data, and they order the close years differently.
- The 10 warmest years in NOAA's 176-year record have all occurred since 2015; Berkeley Earth counts 11 straight years, 2015 through 2025, among its own warmest on record (NOAA NCEI; Berkeley Earth).
- 2024 is the first calendar year confirmed above 1.5°C over the 1850-1900 pre-industrial average, at 1.60°C per Copernicus and 1.55°C in WMO's blended estimate. Eleven of its twelve months topped 1.5°C in the Copernicus data, with July 2024 the single exception (Copernicus/C3S; WMO).
- A record year is not the same as breaching the Paris Agreement's 1.5°C goal, which tracks a multi-decade average rather than any single year. The 2023 to 2025 three-year average is the first three-year stretch on record to top 1.5°C (WMO; Copernicus/C3S).
- NASA's own GISS figures put 2025 a fraction of a degree ahead of 2023 for second place; NOAA, Copernicus, Berkeley Earth, and the UK Met Office's Hadley Centre all rank 2023 ahead of 2025 instead, a gap that sits inside every agency's stated margin of error (NASA GISS; NOAA NCEI; Copernicus/C3S; Berkeley Earth).
- NOAA's Climate Prediction Center placed the Pacific in an El Nino Advisory in its July 9, 2026 outlook and put the chance of a very strong El Nino by October through December near 81 percent, a reversal from the cooler conditions forecasters expected for 2026 at the start of the year (NOAA CPC).
- A multi-agency synthesis reported by Carbon Brief around the same time put the chance of 2026 beating 2024 for the outright record near 19 percent and the chance of a second-place finish near 62 percent. Both figures keep moving while the El Nino strengthens (Carbon Brief).
How the price reflects the chance of a record.
Where to trade: Kalshi lists its temperature and climate contracts to US persons under CFTC oversight. Polymarket's blockchain markets are geoblocked to US persons and trade internationally instead. Check eligibility before funding either account.
Reading the hottest-year brackets: Polymarket's six brackets, from hottest down to sixth or lower, are one probability distribution over where 2026 lands rather than six separate yes-or-no contracts. The brackets together sum to the market's complete view. Watch weight shift between the top brackets as new monthly data and ENSO updates land, rather than reading any single bracket alone.
The Polymarket and Kalshi gap: Both platforms settle on the same NASA GISS data, so a price gap between them is not a disagreement about the temperature. The gap is a liquidity artifact: the two venues share no order book and no user base, and the Kalshi mirror has traded with a thin, largely one-sided book while the Polymarket brackets carry continuous two-sided depth. No trader can buy the cheap side on one venue and sell the rich side on the other, so the gap can sit open with no factual dispute behind it.
How the daily city brackets work: Kalshi opens a fresh set of brackets for each city every day, covering the plausible range of that day's high. Only the bracket holding the actual measured high resolves Yes; every other bracket that day resolves No at the same moment. Trading stays open until 11:59pm local time, but a daily high in a coastal or desert city often lands hours earlier in the afternoon, so by evening the outcome can already be decided even as the brackets keep trading. Check that day's observed high, not just the forecast, before taking a position late.
Why the settlement source matters: Read the contract's rules text, not the market title. "Highest temperature in Los Angeles" settles on one named station, LAX Airport, not a citywide average or a forecast model. The hottest-year brackets settle on NASA GISS specifically; NOAA and Copernicus publish their own rankings from overlapping data using different base periods, and can rank a close year differently. A price only makes sense once you know which dataset decides it.
The CO2 and 2C contracts read differently: The CO2 brackets settle on Mauna Loa's monthly average from NOAA's Global Monitoring Laboratory, not the annual mean or the smoothed trend line, so one high or low month can move a bracket before the broader trend does. The 2C warming contract needs the annual global mean over the 1850-1900 baseline to cross 2.0C, confirmed by the major datasets, not one preliminary estimate or one hot month.
Honest limits: The annual and monthly climate contracts settle with a lag by design. The hottest-year brackets can sit open for months after 2026 ends, waiting on NASA's January data release, with a hard fallback into 2027, so a position taken today ties up capital until then. None of these markets measure damage, cost, or how a heat wave felt. They measure one published number against one published rule, and that is the only thing a payout tracks.
heat and temperature prediction markets.
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