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Kalshi resolves daily-high temperature contracts using the official NWS Daily Climate Report (CLI) for the named station. The "day" runs from 1:00 AM local standard time to 12:59 AM the following day, year-round, meaning during DST, the contract window is offset one hour from the clock time you're reading. The CLI report typically posts the morning after the contract day. Settlement is final on the published value, with rare exceptions for preliminary-vs-final report mismatches.

39 mph sustained winds = named/tropical storm threshold. 74 mph = hurricane (Cat 1). 111 mph = major hurricane (Cat 3). For contract resolution, what matters is the official NHC classification at the moment specified by the contract, at landfall, at peak, or during the resolution window, not common usage.

Polymarket defines landfall as "the hurricane's surface center intersects with the coastline." If the storm passes through a strait between two islands without the eye crossing land, it can resolve NO even if both islands experience hurricane-force winds. This is a real disputed edge case, see the 2025 Bahamas market on IBKR.

It depends on the contract shape. Polymarket has historically run deeper liquidity on basket-style season-total contracts (named storm counts, ACE thresholds, US Cat-4/Cat-5 landfall). These draw consistent volume because they let traders express a single view on the whole season. Kalshi runs region-specific landfall contracts (Miami, Orlando, Gulf, Carolinas) and named-storm-count series with thinner per-contract volume but tighter resolution language. Rule of thumb: basket-trade the season → Polymarket. Trade a specific resolution edge case → Kalshi. The Resolution Calendar above shows live volume per contract. Check it before sizing.

The contract's resolution language always names the station. Read it once when you list. The cohort phrase: "all of this is public and it is on you to find it." On this page, every contract row exposes its resolution station/source, no clicking through.

ACE = Accumulated Cyclone Energy. A single number summarizing total tropical activity in a season, calculated from the wind speeds of every named storm. ACE is more stable than named-storm count because it's not vulnerable to a busy-but-weak season distorting the number. Polymarket's ACE-bracket contracts (≥ 125, ≥ 175, etc.) are favored by traders who want exposure to season-total activity without being whipsawed by weather-of-the-week.

Conceptually yes, region-specific Kalshi landfall contracts function as parametric hedges. The Insurance Journal piece (March 2026) discusses this use case explicitly. Practically, the contract sizes are too small for institutional hedge purposes, and resolution edge cases (city-vs-region landfall definitions, wind-speed thresholds) need careful reading. Treat as supplemental position, not primary cover.

CSU's Klotzbach team publishes seasonal Atlantic hurricane forecasts four times a year: an initial outlook in early April, then revisions in early June, early July, and early August. The June update is the first regular-season revision and historically the most market-moving. It's published around 8 AM Eastern. Contract prices typically move within minutes. The Resolution Calendar above lists each CSU update and the contracts it most affects.

Monthly snowfall totals are subject to revision in NWS daily reports, preliminary numbers can change over the month. NOWData publishes the verified monthly summary on the first business day of the month following the contract window. Kalshi resolves on this verified number to avoid mid-month preliminary-vs-final disputes.

In the April 2026 CDG hair-dryer incident, Polymarket migrated its Paris resolution source from CDG to Le Bourget on April 19, but did not unwind the manipulated contracts. Settlement on a corrupted source typically holds unless the platform proactively unwinds, which is rare. The single-point-of-failure problem persists across every weather market on both platforms; this is why station selection and resolution-source review are core to the cohort workflow.

First-named-storm contracts on either platform resolve YES on the first NHC advisory designating a named storm in the specified basin (typically Atlantic) between contract listing and the stated deadline. Resolution source is the NHC Tropical Cyclone advisory archive. If no storm is named by the deadline, the contract resolves NO at midnight when the window closes. Settlement is automatic on Kalshi against the advisory; on Polymarket, an UMA proposer files the outcome within 24 hours unless disputed. NHC reanalysis after the fact does not change settlement. The original advisory is what counts.

Polymarket's Cat 5 landfall contract resolves on the initial advisory: "regardless of any later retraction or analysis." This means a borderline storm can settle YES in real time and later be reanalyzed to Cat 4 in the post-season Tropical Cyclone Report, settlement still holds. Kalshi region-specific contracts often resolve on the post-storm hurricane report, which uses the final analysis. Read the contract language to know which.