Can an AI agent beat Kalshi's Miami high temperature market?

From a rule to a record

A backtest of a Miami temperature rule tells you what it would have done against prices already known. This page wants the other thing: how the idea that Miami's steady highs make the 1 PM favorite worth its price fares against the KXHIGHMIA book as it stands, each day at 1:00 PM Eastern, filled at the ask, charged Kalshi's fee (about 0.8¢ a contract at 86¢), and settled when the CLIMIA report says so. So the Miami agent runs on Windmill like any user's agent, and each bet it places on KXHIGHMIA is written here as it settles, wins and losses alike.

How the agent works

The agent is the rule below in plain English, on Claude Haiku 5.5, scheduled once a day, at 1:00 PM Eastern. It builds its record in four steps.

1. Read the ladder

Every day at 1:00 PM Eastern, it reads today's KXHIGHMIA ladder, bracket by bracket, with the live ask on each. A KXHIGHMIA day in the facts below had 6 brackets, listed about 39 hours before the ladder closes at 1:00 AM Eastern time. It can also open the National Weather Service's forecast and the latest reading at Miami International Airport from api.weather.gov, public pages its fetch tool reads.

2. Filter for the setup

It places nothing unless both of these hold:

• the highest-priced bracket asks 80–92¢
• the latest KMIA observation (api.weather.gov/stations/KMIA/observations/latest, °C converted to °F) is not above that bracket's top

Why this setup: Miami's official highs below moved a median of 1°F from one day to the next, so by 1 PM the ladder usually has a clear favorite; the rule buys it at 80–92¢, and only while the airport's latest reading hasn't already passed the bracket.

3. Size and place

It buys 5 YES on it at the ask, on paper against the live KXHIGHMIA book: a paper order fills only against what the book shows at that price. At about 86¢ a contract, Kalshi's taker fee at KXHIGHMIA's settings (fee type "quadratic", multiplier 1) is about 0.8¢; the 80–99¢ favorites in the price table below paid 0.6¢ on average. So the five contracts cost about $4.34 all in, and pay $5.00 if they win.

4. Hold to settlement and record it

Every position is held until Kalshi settles the day on Miami International Airport's official reading, the National Weather Service report CLIMIA as The Weather Company reports it, a median 6.2 hours after the ladder closes. The price paid, the fee, the result and the net go into the record below as each bet settles. Most of the daily runs end with no order, and the agent's log keeps those too.

The record: October 30, 2026

Started October 29, 2026; no settled bets yet.

Nothing is read into the record before thirty settled bets.

It runs this page's starter rule, word for word:

“Every day at 1:00 PM Eastern, on today's KXHIGHMIA market: if the highest-priced bracket asks 80–92¢ and the latest KMIA observation (api.weather.gov/stations/KMIA/observations/latest, °C converted to °F) is not above that bracket's top, buy 5 YES on it at the ask. Otherwise no order. Hold to settlement.”

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The market the rule is betting into

Kalshi's API listed 67 settled Miami days, from Aug 24, 2026 to Oct 29, 2026: 402 brackets, 6 a day in the median, of which 67 won. The official highs ran from 80°F (Thu, Oct 22) to 93°F (Tue, Sep 15), with a median of 90°F, and on 0 of the 67 days the winner was one of the two open-ended brackets at the ends of the ladder. A median day traded 152,471 contracts across its brackets over the last 7 days.

Each day's ladder was listed about 39 hours before it closed, closed at 1:00 AM Eastern time after the day it is about, and settled a median 6.2 hours after the close, once the official reading was in. Trading runs through the afternoon, while the high is still being set: a rule that buys late in the day knows more, and pays for it in the price.

Miami's official highs

The ten newest days:

The daily low (KXLOWTMIA)

Kalshi also lists Miami's daily low as its own series, KXLOWTMIA, on the same station. It settled 67 days from Sun, Aug 23 to Wed, Oct 28, with official lows from 70°F to 82°F. A low is often set in the early morning, so its ladder is a different question from the high's, on the same report.

How the 1 PM favorite did

For each of the 48 newest days up to Oct 29, 2026, we read Kalshi's quote 12 hours before the close and took the favorite, the bracket priced highest, at its ask. 46 had a quote at that moment, and the favorite won 31 of them. Breakeven is the price plus Kalshi's taker fee, as a share of the $1 a winning contract pays.

Three notes on that table. The 80–99¢ band has the widest gap between win rate and breakeven, 90% against 90.0%, and at 20 days its interval runs from 70% to 97%, which includes breakeven. Two of the three bands fell short of breakeven, the 60–79¢ band by the most: 55% against 74.8%. And every band's interval includes breakeven, which is why the last column reads the same three times. In our read of Kalshi's prices, the Miami favorite 12 hours before the close is priced about right. Nothing on this page says a buyer of the favorite has an edge.

The rule under test pays 80–92¢ a contract, which puts it in the 80–99¢ row: there the favorite won 18 of 20 days, against a breakeven of 90.0%. The rule's own conditions are what the record above tests; these rows are only the market's baseline at its price.

Kalshi's rules, in Kalshi's words

This is the rule of the market that was open (KXHIGHMIA-26OCT30-T89) when we read Kalshi's API on October 30, 2026, quoted from Kalshi; the series and its full rules are on Kalshi's site. The day and the bracket's bounds change with every market:

“If the maximum temperature recorded at Miami (CLIMIA) for Oct 30, 2026, is greater than 89° fahrenheit according to The Weather Company, then the market resolves to Yes.”

Kalshi adds, in the same market's rules:

“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 the maximum/minimum temperature as reported by the Weather Company.”

The series names The Weather Company as its settlement source. Kalshi lists the series with the fee type "quadratic" at a multiplier of 1: a taker pays 1.8¢ a contract at 50¢ before rounding, less toward either end, and a resting order that fills later pays nothing. The fee calculator works out the fee and the breakeven for any price.

The rules name the station "Miami (CLIMIA)": the daily climate report the National Weather Service's Miami office issues as "The Miami climate summary" for its Miami International Airport station (KMIA), so the market settles on the airport's reading, as The Weather Company reports it, not on Miami Beach's or downtown's. (NWS Miami, climate report CLIMIA, checked October 30, 2026.)

What success looks like

A positive net per contract after Kalshi's fees over thirty settled bets, with the confidence interval clear of zero, would be a result.

A rule that only matches its price is not one. A contract bought near 86¢ that wins as often as that price says, 86 times in a hundred, loses about 0.8¢ a contract to the fee alone (the 80–99¢ favorites in the price table paid 0.6¢), so the line to beat on KXHIGHMIA is a win rate of about 86.8%, not 86%. Each win at that price nets about 13.2¢ a contract after the fee and each loss costs 86.8¢, so one loss takes 6.6 wins to cover.

The rule runs once a day, so thirty settled bets take at least 30 days, and longer when the setup is rare. If the record climbs, the idea that Miami's steady highs make the 1 PM favorite worth its price holds at these prices. If it falls, the idea goes, and the record stays on this page.

Follow along

• This page refreshes every hour from Kalshi's settled data and the agent's own log.
• Copy the Miami agent: the button below opens the builder with this KXHIGHMIA rule, to run as written on paper under your own account, or with your own numbers in place of 80–92¢.
• The fee calculator shows the fee and the breakeven at any price on KXHIGHMIA.
• The 90-strategy test is the longer version of this exercise: about 90 rules and 4,200 paper bets across ten days.
• The Kalshi markets hub lists the other weather cities and every other market page.

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Questions

What does Kalshi's Miami high temperature market settle on?

On the day's maximum temperature at Miami International Airport, as The Weather Company reports it; the rules name the station MIA report (CLIMIA). Exactly one bracket of the day's ladder wins.

What is the fee at 50¢?

A taker pays 1.8¢ a contract before rounding at 50¢ on this series (fee type "quadratic", multiplier 1), less toward either end. The fee calculator gives the fee and breakeven at any price.

Is a bot here profitable?

Nothing on this page says so. The favorite 12 hours before the close won 31 of 46 days in our read of Kalshi's prices, and the table shows each price band against its breakeven: 3 of its 3 bands are inside noise. Run your own rule on paper to see what it does, before you risk money.

Paper or live?

Agents trade on paper unless you build them live. Paper orders fill against Kalshi's live order book with Kalshi's fees and settle when the real market settles. To trade real money, connect your own Kalshi API key and build a live agent; your money stays on your Kalshi account.