Updated October 6, 2026.
Contents
Miami’s routine temperature readings reached 70°F on January 20, 2025, yet NOAA’s archived daily high was 73°F despite a routine reading in every hour.
That difference can matter for a temperature contract because a chart of the station’s hourly temperatures does not necessarily show the value in the contract’s named report. Polymarket US names Miami International Airport as its Miami station and the National Weather Service’s Daily Climate Report as its settlement source. PM-US weather FAQ
But “hourly data misses the high” is too broad: the same Miami archive contains a midnight report with a separate maximum-temperature remark of 73°F. The information was there in a different field.
How often did the fields differ?
To see how often the fields differed, I compared a full year of NOAA records at all five stations in the current PM-US weather FAQ: Central Park, Midway, Miami International, San Francisco International and Los Angeles International.
For each eligible date I compared the highest routine current-temperature reading with the archived daily maximum after converting both to whole degrees Fahrenheit. Each date needed readings in at least 23 distinct hours and checks for conflicting records and inconsistent timestamps.
The daily maximum exceeded the highest routine reading on 202 of 344 dates at Central Park and 186 of 352 at Midway. The corresponding counts were 241 of 350 at Miami, 234 of 351 at San Francisco and 233 of 352 at Los Angeles.
Across the stations that is about 53% to 69% of eligible dates. The usual positive difference was 1°F, though gaps of 2°F or more occurred on 6% to 15% of eligible dates depending on the station. Restricting the comparison to dates with readings in all 24 hours barely changed those percentages, so missing an entire hour does not explain the result.
These comparisons within NOAA’s historical archive are not counts of incorrect settlements. Two dates also ran in the opposite direction with the routine reading exceeding the archived high. The methods retain those cases and disclose the data checks. Data and methods
The report contains more than one temperature
A routine METAR reports weather at a particular time, with a current-temperature field that describes conditions around that observation. The daily high can occur between observations. In the Miami example the highest routine reading of 70°F came at 12:53 a.m., but the archived daily high does not record when the 73°F occurred.
Some METARs also contain maximum-temperature remarks that answer different questions from the current-temperature field. Six-hour maxima appear in reports associated with 00, 06, 12 and 18 UTC, while a separate daily maximum appears in the local-midnight report. ASOS manual, section 3.1.2
The midnight maximum remarks matched far more often in this sample. On dates with an eligible midnight maximum remark, that remark matched the archived daily high on over 99% of dates at each station. At Midway the current-temperature maximum matched on 165 of 351 dates compared with 348 of those same 351 dates for the midnight maximum remark.
Those close matches do not remove the limits of a maximum remark. The midnight report usually leaves a few minutes before the climate day ends, and the archive contains conflicting values including eight disagreements between midnight remarks and daily highs across the five stations. The remarks are useful evidence but do not replace the contract’s named report. The PM-US FAQ names the 24-hour METAR observation as a cross-check. If the CLI reading is inconsistent with it, settlement can be delayed until 11 a.m. ET for review. PM-US weather FAQ, ASOS manual, methods
A maximum also needs a time window
The Miami example shows why the window matters as well as the field. At 12:53 a.m. local standard time on January 20, a six-hour remark reported a third value of 78°F. Its window runs from about 7 p.m. on January 19 to 1 a.m. on January 20. A 6:53 p.m. reading on January 19 also showed 78°F. Assigning that entire maximum to January 20 because of the report’s date gives the wrong window.
The climate day follows local standard time throughout the year, so during daylight saving time its midnight-to-midnight period corresponds to 1 a.m. to 1 a.m. on the local clock. A midnight cutoff in a chart can therefore select the wrong period. NWS climate instruction, section 4.1.2
Start with the contract’s report
The PM-US FAQ links Miami to the NWS CLIMIA report. In the copy retrieved on October 4, the report gave a maximum of 87°F for October 3 with the date in its heading and Fahrenheit identified in its temperature table. NWS Miami CLI
The filed contract template distinguishes “above” from “at least.” Applied to 87°F, an illustrative “above 87°F” condition is false while “at least 87°F” is true. These examples explain the operators without making claims about an actual listed contract or its settlement. PM-US temperature terms
The particular contract also determines which publication counts as final. Because NWS climate reports are preliminary and can change through later quality control, a subsequently downloaded NOAA archive is not proof of the value originally used for settlement. NWS observations FAQ
For a daily temperature contract, verify the station, field, observation period, report version and comparison operator. More frequent readings help only when they measure the quantity the contract asks about.
This study measures an established reporting distinction at five stations in 2025. See Splitrule’s data and methods.