Highest temperature in Seattle on July 23?

Platform comparison

Market context

Seattle-Tacoma International Airport’s highest temperature on 23 July will be set by the day’s observed maximum in degrees Fahrenheit, not by a forecast or citywide average. Seattle’s July climate is usually mild, with typical highs around 73–75°F and comparatively dry conditions, so a late-July outcome generally depends on whether a warm ridge builds over western Washington or marine air keeps the airport capped in the low-to-mid 70s.[1][4]

That makes the current **0% YES** implied probability on the market hard to read at face value: on Polymarket, the quoted probability is the market’s own percentage, whereas Kalshi and Betfair-style books are usually easier to compare via decimal odds and their embedded margin or commission. Smarkets is also useful as a benchmark because it typically displays decimal prices with a separate commission layer, while access and settlement frictions differ by venue, especially for KYC and jurisdictional reach; for a Seattle temperature event, the main practical issue is less the contract logic than how much liquidity each venue can attract into a niche weather line. Historical context from NOAA’s Sea-Tac station data shows this airport has a long, low-volatility July pattern, so a summer high in the 70s is the baseline rather than an outlier.[2][1]

Traders should watch the Seattle-area forecast for the 23rd, but also the broader synoptic setup: cloud cover, onshore flow and marine layer depth can suppress the maximum more than headline “hot day” forecasts suggest. The contract settles from the Seattle-Tacoma International Airport station record on Wunderground, so nearby downtown warmth matters only if it reaches Sea-Tac itself; the relevant comparison is the airport observation, not the city proper.[2]

Sources: 1 · 2 · 3 · 4

Methodology

This page compares Highest temperature in Seattle on July 23? 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

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

Polymarket vs Kalshi — which is better?

Depends on your location. Kalshi is CFTC-regulated, US-only with full KYC. Polymarket is global, on-chain, no KYC up to $1,500. Polymarket has ~10x higher liquidity but higher regulatory risk.

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.