Highest temperature in Seattle on August 4?

Platform comparison

Market context

Seattle-Tacoma International Airport’s highest temperature on 4 August is what will settle this market, so the main question is whether the day finishes in a warm but ordinary late-summer band or breaks into an unusually hot reading. Polymarket’s contract is already pricing a near-lock on the 80-81°F range, while the quoted crowd-implied probability on this venue remains at 0% YES, which is a reminder that different books can display the same event very differently because one may show range-by-range prices and another a single binary yes/no view. [2]

Seattle’s early-August climatology usually supports highs in the upper 70s to low 80s, and AccuWeather’s August outlook for Seattle shows 81°F as the daily high on 4 August with a 62°F low, which makes a mid-80s or hotter outcome look less likely than a result near the published forecast. That fits the platform-comparison angle: on Polymarket, traders can express that view as a specific temperature bucket, while on Kalshi or Smarkets the same judgement would be translated into decimal-style pricing and, depending on the venue, different fee and access constraints; Betfair also tends to matter here because its exchange model and KYC/geographic reach can change effective liquidity even when the underlying weather thesis is the same. [1][2][3]

For traders, the key catalysts are the morning forecast updates, any marine-layer breakdown or inland heat push, and the first official KSEA observations that can lock in the day’s high before the next day’s datapoint is published. The market description says Wunderground at Seattle-Tacoma International Airport is the settlement source, so late revisions matter only until the first datapoint for 5 August appears; after that, alterations are excluded. That means the practical watchlist is the National Weather Service forecast cycle, airport observations through the afternoon, and any platform-specific rules on finality, KYC, and fees that affect whether a small move in temperature is worth trading on Polymarket versus Kalshi, Betfair, or Smarkets. [2][7]

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 Kalshi Alternative, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Polymarket settles via UMA Optimistic Oracle on Polygon. A proposer posts the outcome with a bond, the two-hour window runs, then the smart contract pays USDC.

Kalshi settles USD through the CFTC-regulated clearinghouse — the cleanest variant, with heavier KYC. Betfair Exchange settles in account currency (GBP/EUR), net of 2-5% commission. Smarkets follows the same model as Betfair with a lower default 2% commission.

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.

What about Smarkets as an alternative?

Smarkets is a UK betting exchange with a lower default commission (2%) than Betfair. Liquidity on political markets is below Polymarket, comparable to Kalshi. Geo-blocked in many jurisdictions.

Which platform is accessible globally?

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

Are all these platforms regulated?

No. Kalshi is CFTC-regulated (US). Betfair and Smarkets are UK Gambling Commission licensed. Polymarket operates without explicit regulation — a different risk profile than a regulated sportsbook.

Which platform supports Klarna/SOFORT?

Directly: none. Polymarket accepts only USDC on Polygon. Kalshi Alternative 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.