The terms that decide whether a weather market is read correctly. Each definition stands on its own.
A prediction market whose outcome is decided by a published weather measurement, such as the highest temperature at a named station on a given day.
Unlike a forecast, it settles on an observation that has already been recorded and published by an official source. On Polymarket the tradeable weather variables are daily high and low temperature, monthly rainfall total, and daily PM2.5 air quality.
The single weather station whose official reading decides a weather market, named in the market's own rules and identified by its ICAO code.
It is not a city average and not the nearest station to the city centre. Two stations in one city can differ by more than a full bucket on the same afternoon. The station is the market's decision and can change.
One outcome in a weather market, covering a range of the settling measurement, for example 23C or 86-87F.
Polymarket temperature buckets are one degree wide in Celsius cities and two degrees Fahrenheit in United States cities. The bucket is decided on the rounded official figure, so a reading of 24.6 published as 25 settles the 25 bucket.
The period a weather market measures, running midnight to midnight in the settlement station's own timezone.
It is not the trader's local day. A market titled for one date can still be open while it is the previous day where the trader is, which is the most common way these markets are misread.
The highest or lowest value recorded so far during the settlement day.
It is monotone: a daily high only rises and a daily low only falls. Before the afternoon peak a running maximum says very little, because the day can still climb past it. After the peak has passed the day's high is effectively fixed even though the market has not settled.
The market price of a bucket read as the probability that bucket settles, since a winning share pays one dollar.
A bucket trading at 0.30 implies a 30 percent chance. Across a full set of buckets the implied probabilities sum to slightly more than one, and that excess is the market's spread.
An estimate of what a weather measurement is right now, between the official station's scheduled reports.
Official stations publish at intervals, so between reports the true current value is unknown. A nowcast fills that gap. It is an estimate and never replaces the official reading a market settles on.
The average size of a forecast's misses, ignoring direction, in the unit being forecast.
An MAE of 0.5C means that on average the forecast was half a degree away from the settled reading, whether too high or too low. It is the standard way to state how wrong a temperature forecast usually is.
Every city currently traded and the station that settles it is on the settlement station table, also available as JSON.