Question 1

How do weather betting markets work?

Accepted Answer

Kalshi and Polymarket both list daily contracts on a city's high temperature for a single day. Each contract covers one bucket, such as 85 to 86 degrees Fahrenheit or 90 degrees and above, and the market price reflects the probability traders assign to that bucket happening. Contracts typically open about a day and a half before the measurement day and close near midnight. Kalshi settles once the National Weather Service publishes its daily climate report for the station the next morning. Polymarket settles on the highest hourly observation NOAA recorded at its station that day, which can sit a degree or two under the climate report's maximum because the hourly column misses the between-hours peak. GhostLeg also tracks and grades the daily-low markets, but the board shows daily highs only.

Question 2

Which station settles each city?

Accepted Answer

Every city on this page settles against one specific National Weather Service reporting station, not the whole metro area, and the two venues do not always pick the same one. Kalshi and Polymarket share the station in seven of the eleven cities both list. They differ in four: New York (Central Park for Kalshi, LaGuardia for Polymarket), Chicago (Midway and O'Hare), Denver (Denver Intl and Buckley Space Force Base) and Dallas (Dallas-Fort Worth and Love Field). Every station card's settles line names each venue's station, and the city detail's venue note adds the source each venue uses.

Question 3

Why do Kalshi and Polymarket disagree on NYC?

Accepted Answer

Kalshi settles New York against Central Park. Polymarket settles against LaGuardia. Central Park sits inland with tree cover that runs a degree or two cooler on hot afternoons, while LaGuardia sits on open pavement near the water and tends to run warmer. Since the two venues are reading different thermometers, their contracts can honestly price different outcomes on the same day without either one being wrong. The two venues also carve different two-degree buckets in some cities, so a price on one venue can have no twin on the other; the card then compares their expected highs instead.

Question 4

How do you compare the venues when their buckets do not line up?

Accepted Answer

Polymarket's two-degree buckets always start on an even degree. Kalshi's start wherever it centred that day's ladder, so on many days the two ladders are offset by a degree and no bucket is shared. When Kalshi's top bucket is listed on both venues, the card's notch shows the cents gap on that bucket. When it is not, the notch shows the expected-high gap: each venue's price-weighted bucket midpoint, in degrees, with the two tails counted half a degree past their edge. The card's footer shows both expected highs on every day, and GAP FIRST sorts the board by that gap in degrees.

Question 5

How accurate are Kalshi weather markets?

Accepted Answer

The Record section on this page tracks it directly: every graded contract's price band against how often that band actually happened, with the sample size published next to every point. A well calibrated market lands close to the diagonal reference line, where a band priced around 70 cents hits close to 70 percent of the time. We publish this chart continuously rather than a single historical number, since accuracy varies by price band and by venue.

Question 6

What is the GhostLeg model, and how has it done?

Accepted Answer

GhostLeg runs a market-blind intraday model for every city: it reads the running maximum, the day-ahead forecast ensembles and a fitted per-station hour-of-day curve, never a market price, and quotes a probability for each bucket every ten minutes. It is scored in public against Kalshi at a fixed 9 AM local standard time decision hour, inside each city's detail. On every read so far it has not beaten the market, which is why the board shows the two venues and their gap rather than a model call.

Question 7

The climate day rule (local standard time)

Accepted Answer

A city's climate day always runs midnight to midnight in that city's local standard time, not local clock time. During daylight saving time this means the measurement window actually runs 1 AM to 1 AM on the clock, because the official National Weather Service climate day never shifts with the clock change. Getting this boundary right matters: get it wrong and an hour of the wrong day's temperatures leaks into a contract's grading.

Every city has two thermometers. We track the gap.