How Kalshi's Rain Markets Decide It Rained
Kalshi rain markets do not answer the question "did it rain?" They answer a narrower one: does the official precipitation ledger, kept by one named data provider for one named station, show a total strictly greater than 0 inches? Those are different questions, and the gap between them is the cleanest example anywhere on the exchange of why "what settled" and "what happened" can disagree. You can stand under a drizzle, feel it on your face, watch it bead on your windshield, and still hold a contract that resolves No. Nobody cheated you. Every reason it happened was published in the rules before you ever clicked buy, and by the end of this article you will be able to explain each one.
The Quick Answer
How does Kalshi decide if it rained? Each rain market settles Yes only if the official daily precipitation total for the named settlement station, as reported by The Weather Company, is strictly greater than 0 inches; trace amounts and missing values both count as 0. That means a day with visible, felt-on-your-skin rain can settle No. The rule that makes it possible, the company doing the counting, and a worked example of the drizzle that settles No are all below.
The Bar: Strictly Greater Than 0 Inches
A rain contract is a yes/no question that settles at $1 or $0, a CFTC-regulated event derivative whose price trades in cents that read as a probability; the general mechanics are covered in our explainer on how prediction market contracts work. What is specific to rain is the resolution condition, and it is a single number: the day's precipitation total must be strictly greater than 0 inches. Not "rain was observed." Not "the ground got wet." A recorded total above zero, full stop.
A bar that low sounds like a formality. It rains, the total is more than zero, Yes wins, surely. But the bar only means something once you know what counts as zero, and that is where this market stops being intuitive.
The Trace Rule Is The Whole Page
Here is the sentence from the market rules that decides more close calls than everything else combined:
"Trace amounts (T) and missing daily precipitation values are counted as 0 inches."
A trace, written as "T" in an official climate report, is real rain that never accumulates to 0.01 inches, the smallest increment standard precipitation reporting records. The gauge got wet; the ledger has no number to write down. Official climate reporting has used this convention for a very long time, and for meteorology it is a sensible one. For a contract holder it is the entire game: a trace is not a small amount of rain that rounds down. It is defined as zero.
Put the two rules side by side and the surprising outcome falls out on its own. The market needs a total strictly greater than 0 inches. A trace counts as 0 inches. So a day of visible, measurable-to-the-eye drizzle, the kind that has everyone's wipers on, can produce an official value of T and a settlement of No. The trader who watched it rain and the exchange that paid out No are both right, because they were answering different questions. This is the precipitation cousin of the settlement station trap in the temperature markets: there, the number is real but comes from a different thermometer than you were watching; here, the rain is real but the ledger calls it zero.
Missing Data Also Counts As Zero
Read that quoted sentence again, because it contains a second rule hiding behind the first. Missing daily precipitation values are also counted as 0 inches.
That is a structural asymmetry worth naming plainly. If the settlement value simply never gets reported, the market does not void, does not refund, and does not wait. A reporting gap resolves the same direction a dry day does: toward No. The two outcomes "it did not rain" and "the data did not arrive" are indistinguishable at settlement.
We are describing a mechanic, not handing you an angle. Nothing about this asymmetry tells you which side of any market to be on, and we are not suggesting one. The asymmetry is simply a term of the instrument that a holder should know before owning either side, the same way a bond holder should know what happens on a missed coupon. The rules chose a convention for the bad-data case, they published it in advance, and the convention is No.
Who Does The Counting: The Weather Company, Not The NWS
If you have read about how Kalshi's temperature markets settle, you know the National Weather Service's daily climate report is the source there. It would be natural to assume the same government feed decides rain. It does not, and the assumption is worth killing carefully, because this is exactly the kind of detail that separates reading the instrument from reading the sky.
The binding rules of the rain markets point to The Weather Company, at weather.com/kalshi, as the settlement source. The confusing part is that the station is still named with an NWS-style climatological identifier, a CLI code like CLISFO for San Francisco or CLISEA for Seattle. The identifier and the provider are not the same thing. The station code tells you where the measurement is taken; The Weather Company is who reports the official value the contract grades on. A government-looking code on the label does not make it a government feed.
Kalshi says this itself, and quoting them is stronger than us asserting it:
"Not all weather data is the same. While checking a source like AccuWeather or Google Weather may help guide your decision, the official and final value used to determine this market [is] as reported by the Weather Company."
That is the exchange telling you, in advance, that your weather app is a decision aid and not the referee. One sourcing note for anyone who goes digging: the family-level contract PDF for the rain markets is a template that literally reads "The Source Agency is <source>", with the placeholder unfilled. The binding language lives in each individual market's own rules text. If you want to verify any of this, and you should want to, read the rules on the specific market you are trading, not the family document.
A Worked Example: The Drizzle That Settles No
Walk through a representative gray day at a coastal station, with illustrative numbers, and watch where each question gets answered.
| The Question | Who answers it | The answer |
|---|---|---|
| Did Water Fall From The Sky? | Your eyes, all afternoon | Yes, on and off for hours |
| What Does Your Weather App Show? | A blended metro feed | Drizzle icon, "light rain" |
| What Does The Official Ledger Record? | The Weather Company, for the named CLI station | T (trace) |
| What Total Settles The Market? | The rules: T counts as 0 inches | 0.00 |
| Does 0.00 Exceed The Bar Of "Strictly Greater Than 0 Inches"? | The resolution rule | No |
A trader who bought Yes at 60 cents on the morning of that day loses the full 60 cents per contract, and the row I keep coming back to is not the last one. It is the third. The moment the ledger wrote T, every later row was already decided, because settlement is not a poll of the people who got rained on. It is one recorded value, from one named provider, run through two published conventions. The eyes in row one and the ledger in row three never disagreed about the weather. They disagreed about what counts, and only one of them is in the rules.
Settled Means Settled: Revisions Do Not Reopen A Market
One last convention completes the picture. Under the exchange-wide rule, revisions after expiration are not accounted for. Climate data does get corrected; providers occasionally restate a daily value after the fact. If that correction lands after the market has expired and settled, the settlement stands. A later revision does not reopen the market, claw back payouts, or flip a No to a Yes.
This is the same philosophy as the trace rule and the missing-data rule: the market buys finality by naming, in advance, exactly one value at exactly one moment as the answer. Every convention in this article trades a little bit of "what really happened" for a lot of "no arguments afterward." That trade is what lets a binary contract exist at all.
The Shape Of The Risk, And Where We Sit
We should say plainly where we stand. Stokastic trades Kalshi's weather markets and holds positions in them; where a settled position is described anywhere in this series, we were the seller. We publish our settled results, losses included, on our Kalshi weather markets hub, and that log is an open test of an unproven approach, not a track record.
The risk shape is the part we most want a new reader to carry out of this cluster. Selling an unlikely outcome collects a small premium and risks most of a dollar, and roughly speaking, one loss erases the premiums from thirty or forty wins. That arithmetic, not the hit rate, is what makes position sizing the whole game. A trader who learns the trace rule the hard way, on a day the sky and the ledger disagree, is exactly the one loss that arithmetic cannot afford. Understanding the conventions in this article is not an edge; it is the minimum standard of knowing what you own.
The Ledger Is The Weather, As Far As The Contract Cares
Zoom back out to where we started. A Kalshi rain market never asks whether it rained. It asks whether one company's official precipitation value for one station exceeds zero, under a convention where trace rain and missing data both count as zero, judged once, with no do-overs after settlement. Every surprising outcome this market can produce, including the drizzle that settles No, follows from those published sentences. The reader who internalizes that stops experiencing settlement as a verdict on their eyesight and starts reading it as what it is: a contract doing exactly what its terms said it would do.
That habit, pricing the instrument as written instead of the event as felt, is the most transferable skill in this whole space, and it does not stop at weather. A point spread posted at -110 on both sides at DraftKings or FanDuel bakes in an overround of about 4.8%, which works out to roughly 4.5% hold; you only see the fair price once you de-vig it, the same way you only see the real settlement number once you read the trace rule. The same reflex is why line shopping and odds comparison work at all: two prices on the same outcome only mean something once you read both as probabilities. On Kalshi, the fine print doing that work might be a settlement station, a fee schedule, or a regulator's actual jurisdiction. And if you would rather watch probability-first thinking applied to games while you get comfortable with it, our free expert picks are a no-cost place to see the same discipline in action every day.
FAQ: Kalshi Rain Market Settlement
How does Kalshi decide if it rained? A rain market settles Yes only if the official daily precipitation total for the named settlement station is strictly greater than 0 inches, as reported by The Weather Company. Anything else, including a trace, settles No.
What is a trace, and why does it settle No? A trace ("T" in the official report) is rain that fell but never accumulated to 0.01 inches, the smallest increment standard precipitation reporting records. The market rules state that trace amounts and missing daily precipitation values are counted as 0 inches, so a trace day fails the "strictly greater than 0" bar.
Does the National Weather Service settle Kalshi's rain markets? No. The temperature markets settle on NWS climate reports, but the rain markets' binding rules name The Weather Company (weather.com/kalshi) as the source. The station is identified by an NWS-style CLI code, such as CLISFO or CLISEA, but the identifier is not the provider.
What happens if the precipitation data is revised after the market settles? Nothing. Revisions after expiration are not accounted for under the exchange-wide rule. Once a market settles, a later correction to the underlying data does not reopen it.
Disclosure and fine print. Stokastic trades Kalshi weather markets and holds positions in them; where a settled position is described in this series, we were the seller. We have no affiliate or commercial relationship with Kalshi. Kalshi weather contracts are CFTC-regulated event derivatives traded on a designated contract market, not sportsbook wagers, and a position can lose its full value. 18+, available where Kalshi operates; the risk of loss is real and, on the side we trade, individually large. This series is an open research log of a strategy we have not proven. Nothing here is trading advice, and nothing on this page is a pick, a recommendation, or a comment on whether any market is priced well or badly.
