Highest temperature in Seattle on July 23?

Platform comparison

Market context

Seattle-Tacoma International’s highest reading on 23 July will be set by the day’s actual airport observation, and the market settles against the Wunderground history page for KSEA rather than a city-wide forecast. July in Seattle is usually mild by US standards, with typical highs around 75°F and relatively low rainfall, so the distribution is centred in the low-to-mid 70s rather than around heatwave territory.[1][2]

That makes the current 0% YES price easier to read as a statement about the far upper buckets than about whether the day gets warm at all. On Polymarket, that shows up as implied probability; on Kalshi and similar venues, the same view is usually expressed through contract pricing and decimal-style quotes, so the headline number can look different even when the underlying expectation is similar. Betfair and Smarkets also tend to reflect the market through odds after fees, with the net price depending on commission, while KYC access and account availability can differ by platform and jurisdiction.

For traders comparing books, the main catalysts are not announcements but the weather setup: marine air, onshore flow, cloud cover timing, and any inland heat ridge that can lift afternoon temperatures at Sea-Tac. The key operational point is that the settlement source is the station maximum for the full day, so a brief late-afternoon spike matters more than the morning trend. NOAA’s Seattle-Tacoma time-series station page is the closest public reference for observing how the airport’s temperature evolves intraday.[2]

Sources: 1 · 2 · 3 · 4

Methodology

We read Highest temperature in Seattle on July 23? from four platform perspectives: Polymarket (on-chain CLOB), Kalshi (CFTC-regulated exchange), Betfair Exchange (sports book exchange), Smarkets (peer-to-peer betting exchange). Polymarket's live mid is the canonical probability; the side-by-side columns benchmark fees, KYC, settlement currency and deposit rails so you can choose the venue that fits your jurisdiction and trade size.

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

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.

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.

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 supports Klarna/SOFORT?

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