You excitedly check the weather forecast, think you have a sure win, and bet on a weather market. Then the official data comes out, and it is different from what you saw—or was even revised later. Does your bet still count?
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Core Answer: Yes, but it counts the number you see at first glance
This is a counterintuitive answer: in weather contracts on prediction markets, settlement is not based on the "corrected temperature" but on the original number reported by the data source named in the rules at the moment of settlement.
For most weather markets (especially those relying on NWS data), the settlement rules clearly follow the "raw-as-reported" principle. That means once the data is reported, it becomes final. Even if it is corrected an hour later, the settlement result does not change.
In one sentence: you are not betting on the real weather, but on what the platform's designated data source will report.
How settlement works: two standards, and the data source decides
This matches the rules of many real-world weather markets. The final result depends on an authoritative data source that may be delayed or revised. There are two main cases:
Case A: Based on the "first report" (most Kalshi markets)
The rules are clear: settlement is based on the first observation in the original METAR report (aviation routine weather report). This means:
If a weather station reports 52°F at 12:00 Zulu time and then revises it to 51°F within an hour, the contract is still settled at 52°F.
On Kalshi, settlement usually relies on NWS climate reports (CLI) and may use backup station data or LST (local standard time) data, following a similar logic.
Case B: Based on the "final state" of a designated official source (most Polymarket markets)
This is another common model, and it is the key issue. Polymarket usually relies on a specific authoritative data source (such as the Wunderground website) and uses the final data shown on that site. If the data is revised after being retrieved, the platform will use the updated data.
But there is a huge risk here: platforms can revise settlement rules after the fact. On June 14, 2026, Polymarket issued a "settlement clarification" that overturned an already settled market result, invalidating a 20-year-old student's $35,000 bet and wiping out $3.8 million in positions across 1,838 accounts. This kind of "after-the-fact reversal" is considered a tail risk that prediction markets cannot hedge.
There is a vulnerability in the data chain
This settlement logic creates huge manipulation risk. In 2026, a weather station near Charles de Gaulle Airport (CDG) in Paris showed an abnormal temperature spike that was directly linked to tens of thousands of dollars in bets on Polymarket.
The core of the event is this: a market that settles funds based on a single physical observation is only as strong as its underlying data chain. A single data source, with no cross-verification, redundancy, or anomaly detection, can decide who gets real money.
This exposes the most concrete form of the "oracle problem": real-world data is read by an isolated, imperfect system and used for settlement, and that link contains too many vulnerabilities.
Three direct suggestions for ordinary traders
Find the "settlement source" section: Before placing an order, find and carefully read the specific settlement rules for that market. Is it "NWS climate report" or "Wunderground"? Is it "first report" or "final report"? One word can make a world of difference.
Understand that "data source" is not the same as "real weather": The temperature at Pudong Airport may be 3 degrees lower than in the city center. The main station data at Bao'an Airport may come from surrounding stations. Your feeling and your weather app are not the settlement basis. Only the number from the data source named in the rules counts.
Beware of "after-the-fact reversal" risk: Polymarket's rules include a "settlement clarification" clause that allows results to be changed after the fact. This means you are betting not only on the outcome but also on whether the platform will overturn the result later. There is no hedge for this risk, so be mentally prepared before participating.
Reference cases: different outcomes under two models
| Platform / Market type | Settlement basis | Impact of data revision |
|---|---|---|
| Kalshi weather markets | NWS climate report (CLI), following the "raw-as-reported" principle, based on the first observation report. | Revised data released an hour later will not change the settled result. |
| Polymarket weather markets | Final report from Wunderground or another designated data source, but the platform reserves the right to interpret or revise rules after the fact. | Revised data may change the result, but the bigger risk is that the platform may reverse the outcome after settlement. |
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FAQ
Question: If I see the weather bureau release revised data, can my bet be overturned?
Answer: It depends entirely on the market rules. If it is a Kalshi market based on the "first report," then no. If it is a Polymarket market, theoretically yes, but if the platform issues a "settlement clarification," you could lose even when you originally won.
Question: Why don't platforms settle using the "real weather"?
Answer: "Real weather" is a vague concept and cannot be programmed. To make contracts executable, a clear, verifiable, authoritative data source must be designated. This creates a gap between data and reality, but it is the price of automated contract settlement.
Question: How can I judge whether a weather market's settlement risk is high?
Answer: First, check whether the settlement rules are clear and transparent. If the rules are vague or rely on a single vulnerable data source, the risk is higher. Second, look at the platform's historical reputation. The recent "settlement clarification" issues exposed on Polymarket show a potential risk of after-the-fact reversals, which is much more serious than simple data delays or revisions.
