Highest temperature in Seattle on August 5?

Platform comparison

Market context

Seattle-Tacoma International Airport’s highest temperature on 5 August will be set by the day’s warmest reading in Wunderground’s daily history record, so the market is really about whether the airport tops the low- to mid-80s Fahrenheit band that dominates current forecasting. Across the listed price sources, Robinhood’s climate market had the contract’s upper outcomes clustered around the mid-80s, with 85°F at 83¢ and 86°F/87°F still priced well below that, while weather models and retail forecast pages pointed to a high around 80-81°F to 84°F rather than an extreme spike.[3][1][2][6][10]

That leaves the 0% crowd-implied YES reading as an outlier versus both weather-market pricing and the broader forecast backdrop. For context, Seattle in early August usually sits in the upper 70s to low 80s, and comparable recent daily high markets have tended to concentrate around adjacent temperature buckets rather than a single exact print, which means even modest forecast error can move value between neighbouring ranges.[4][13][14] In other words, the contract is more sensitive to whether the airport nudges above 84°F than to any large directional call on summer heat.

The main catalysts are the late-run forecast updates from the National Weather Service and any heat-advisory language, because those can shift expectations for airport highs even when citywide forecasts remain stable.[5][16] For this settlement source, the key dependency is the actual KSEA reading in Wunderground’s history page, so traders typically watch terminal-area conditions, marine influence, and any afternoon sea-breeze timing more closely than generic Seattle forecasts.[1][16]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

FAQ

Where can I trade this market with the lowest fees?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is Best Prediction Markets. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

How does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

What does Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

How fast are USDC deposits?

Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within minutes.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Best Prediction Markets trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.