Highest temperature in Seattle on August 4?

Platform comparison

Market context

Seattle-Tacoma International Airport’s afternoon high on 4 August is the key number, and the market’s **0% YES** pricing makes the listed outcome look like a pure longshot. On a handicapper’s read, that is the **underdog** side by a wide margin: consensus is effectively saying a very specific temperature band is not where the day will land, while any value case depends on the airport running materially hotter than the crowd expects.

The historical frame is that Seattle’s early-August highs usually sit in the comfortable summer range rather than extreme heat, so the market is leaning towards a middling outcome rather than a spike. Recent forecast-style pages for early August 2026 point to highs around the upper 70s to low 80s Fahrenheit, with one month view showing 4 August around 26°C and another suggesting 81°F for late July, which supports why the consensus is clustered away from the top-end buckets.[1][5][11] The contrarian angle is that if an inland heat ridge builds in western Washington, airport highs can jump several degrees above the base case, and that is where the value spots usually appear in temperature markets.

The main catalysts are the day-ahead and same-day forecast revisions, plus any marine-layer breakup or offshore flow that can push temperatures higher at Sea-Tac relative to downtown Seattle. NOAA’s climate outlook still leans warmer than average for the broader summer, which is supportive of hotter-than-normal days but does not by itself guarantee a specific daily peak.[17] Traders should watch late model runs and any local forecast updates close to 4 August, because the settlement depends on the highest reading recorded at the airport, not the city average or the morning temperature.[8]

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

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

FAQ

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's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

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 Who Will Win trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.