Highest temperature in Seattle on August 4?

Platform comparison

Market context

Seattle-Tacoma International’s highest temperature on 4 August is the settlement variable, so the key question is whether the airport prints into the mid-80s Fahrenheit or stalls a few degrees lower. Polymarket’s contract is already pricing the 84–85°F band at 50%, with 82–83°F at 25% and 86–87°F at 21%, which implies the crowd sees a fairly tight distribution around the low-to-mid 80s rather than a tail event.[2] That framing matters on a cross-book basis: Polymarket shows implied probability directly, whereas Kalshi typically expresses the same view as contract prices around 0–100, and Betfair/Smarkets would translate the view into decimal odds after commission, so the apparent spread can partly reflect fee treatment rather than pure forecast disagreement.[2][9][10]

The historical and comparable-case angle is that Seattle in August is usually warm but not extreme, with monthly climatology clustering around the upper 70s for highs and only occasional excursions into the 80s.[7][8] Current August guidance from AccuWeather shows Seattle around 81°F/62°F on 4 August, while the Polymarket event text cites NWS guidance for low-to-mid 80s under an upper-level ridge.[1][2] On Kalshi, the adjacent Seattle daily high market is effectively pinned near the lower end of its range, which is a useful reminder that different platforms can price the same weather regime differently because of contract design, geography filters, and whether traders are looking at airport highs or city forecasts.[10][9]

For catalysts, the main drivers are the overnight and morning forecast updates, especially any change in the strength or inland progression of the offshore ridge, plus whether marine influence pushes the airport’s realised high below the broader Seattle forecast range.[2][6] Traders should also watch the final hourly forecast cycle on 4 August and the first next-day observation publication, because Polymarket says revisions within the settlement window are counted only until the first datapoint for the following date appears.[2] On the comparison side, access and frictions matter: Polymarket and Kalshi both use US-style event contracts with KYC, but Betfair and Smarkets would usually require marketable order-book liquidity and commission-aware pricing, which can make a narrow weather band like this trade differently even when the underlying meteorology is the same.[9][10]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page compares Highest temperature in Seattle on August 4? specifically across Polymarket, Kalshi, Betfair Exchange and Smarkets. The live probability is the Polymarket mid; the comparison columns summarise each venue's fee structure, KYC, settlement currency and payment rails. Every CTA routes to Robinhood Prediction Markets, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Settlement is the biggest difference between the four platforms: Polymarket on-chain in USDC (instant), Kalshi USD via CFTC (T+1), Betfair and Smarkets in local currency via bank withdrawal (T+1 to T+3). On-chain settlement clears in minutes — the fastest payout path of the four.

FAQ

What does Polymarket cost vs Kalshi?

Polymarket: 0% fees, only Polygon network costs (~$0.01/trade). Kalshi: up to 7% per trade plus spread. For high-frequency traders, Polymarket is dramatically cheaper.

Which platform has the deepest liquidity?

Polymarket — by a wide margin. Top markets reach $50-500M volume, Kalshi ~$200M cumulative, Betfair similar. Deeper liquidity means your trade moves the quote less.

Is Betfair a Polymarket alternative?

Only partially. Betfair Exchange is UK-focused with a sports-betting emphasis; they have politics markets but with thinner liquidity than Polymarket. Settlement in GBP/EUR, 2-5% commission on winnings.

Which platform is accessible globally?

Polymarket is geo-blocked in the US/UK/EU. Kalshi is US-only. Betfair and Smarkets are UK-restricted. Robinhood Prediction Markets has a different geo footprint and routes to Polymarket's order book at 0% fees.

Which platform supports Klarna/SOFORT?

Directly: none. Polymarket accepts only USDC on Polygon. Robinhood Prediction Markets offers a fiat on-ramp via Klarna or SOFORT (DE/AT/CH) and converts internally to USDC for the Polymarket order book. T+1 processing.