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

From a rule to a record

A backtest of a Denver temperature rule tells you what it would have done against prices already known. This page wants the other thing: how the two-bracket idea fares against the KXHIGHDEN book as it stands, each day at 11:00 AM Mountain, filled at the ask, charged Kalshi's fee (about 1.7¢ a contract at 44¢), and settled when the CLIDEN report says so. So the Denver agent runs on Windmill like any user's agent, and each bet it places on KXHIGHDEN 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 11:00 AM Mountain. It builds its record in four steps.

1. Read the ladder

Every day at 11:00 AM Mountain, it reads today's KXHIGHDEN ladder, bracket by bracket, with the live ask on each. A KXHIGHDEN day in the facts below had 6 brackets, listed about 41 hours before the ladder closes at 1:00 AM Mountain time. It can also open the National Weather Service's forecast and the latest reading at Denver International Airport from api.weather.gov, public pages its fetch tool reads.

2. Filter for the setup

It places nothing unless all of these hold:

• the two highest-priced brackets are next to each other
• the higher one asks under 60¢
• their two asks add up to 88¢ or less

Why this setup: Denver's market is often split between two neighbouring brackets in the middle of the day: the 1 PM favorite below cost 40–59¢ on 21 of 48 days. The rule buys both brackets of such a pair when they cost 88¢ or less together, so either one winning pays.

3. Size and place

It buys 5 YES contracts of each at the ask, on paper against the live KXHIGHDEN book: a paper order fills only against what the book shows at that price. At about 44¢ a contract, Kalshi's taker fee at KXHIGHDEN's settings (fee type "quadratic", multiplier 1) is about 1.7¢; the 40–59¢ favorites in the price table below paid 1.7¢ on average. So the pair, 10 contracts, cost about $4.57 all in, and the five of the bracket that wins pay $5.00.

4. Hold to settlement and record it

Every position is held until Kalshi settles the day on Denver International Airport's official reading, the National Weather Service report CLIDEN 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 28, 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 11:00 AM Mountain, on today's KXHIGHDEN market: if the two highest-priced brackets are next to each other, the higher one asks under 60¢ and their two asks add up to 88¢ or less, buy 5 YES contracts of each 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 Denver 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 48°F (Wed, Oct 14) to 95°F (Fri, Aug 28), with a median of 82°F, and on 7 of the 67 days the winner was one of the two open-ended brackets at the ends of the ladder. A median day traded 41,351 contracts across its brackets over the last 7 days.

Each day's ladder was listed about 41 hours before it closed, closed at 1:00 AM Mountain 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.

Denver's official highs

The ten newest days:

The daily low (KXLOWTDEN)

Kalshi also lists Denver's daily low as its own series, KXLOWTDEN, on the same station. It settled 67 days from Sun, Aug 23 to Wed, Oct 28, with official lows from 28°F to 67°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. 48 had a quote at that moment, and the favorite won 30 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, 100% against 88.1%, and at 5 days its interval runs from 57% to 100%, which includes breakeven. Three of the four bands fell short of breakeven, the 60–79¢ band by the most: 67% against 71.4%. And every band's interval includes breakeven, which is why the last column reads the same four times. In our read of Kalshi's prices, the Denver 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 up to 44¢ a contract, which puts it in the under 40¢ and 40–59¢ rows: there the favorite won 11 of 22 days, against breakevens of 2.1% and 53.6%. 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 (KXHIGHDEN-26OCT30-T68) 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 Denver (CLIDEN) for Oct 30, 2026, is greater than 68° 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 "Denver (CLIDEN)": the daily climate report the National Weather Service's Denver/Boulder office issues as "The Denver CO climate summary", which is what The Weather Company's reading follows. (NWS Denver/Boulder, climate report CLIDEN, checked October 28, 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 44¢ that wins as often as that price says, 44 times in a hundred, loses about 1.7¢ a contract to the fee alone (the 40–59¢ favorites in the price table paid 1.7¢), so the line to beat on KXHIGHDEN is a win rate of about 45.7%, not 44%. Each win at that price nets about 54.3¢ a contract after the fee and each loss costs 45.7¢, so one win covers 1.2 losses.

The rule runs once a day and can buy two brackets in a run, so thirty settled bets take at least 15 days, and longer when the setup is rare. If the record climbs, the two-bracket idea 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 Denver agent: the button below opens the builder with this KXHIGHDEN rule, to run as written on paper under your own account, or with your own numbers in place of up to 44¢.
• The fee calculator shows the fee and the breakeven at any price on KXHIGHDEN.
• 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 Denver high temperature market settle on?

On the day's maximum temperature at Denver International Airport, as The Weather Company reports it; the rules name the station DEN report (CLIDEN). 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 30 of 48 days in our read of Kalshi's prices, and the table shows each price band against its breakeven: 4 of its 4 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.