Highest temperature in Seattle on August 5?

Platform comparison

Market context

Seattle–Tacoma International Airport’s highest temperature on 5 August 2026 will be the number that settles this market, and the present 0% implied chance on the top outcome is best read against Seattle’s late-summer baseline rather than against a generic “hot day” yardstick. AccuWeather puts Seattle’s average August high at 78°F, while WeatherSpark’s Seattle history for August 2026 shows a recent airport high of 84.0°F early in the month, which is a useful reminder that a move a few degrees above normal is plausible without reaching extreme territory.[1][2]

The main comparison point is that Sea-Tac’s record heat sits much higher than a typical August peak: FOX 13 Seattle reports the airport record high as 88°F, standing for more than 60 years.[13] That means a settlement band in the low-to-mid 80s remains materially below record territory, but still requires a warmer-than-average afternoon and clear enough skies for a proper climb. The earlier August pattern also matters because WeatherSpark’s airport history already captured an 84°F high, showing the month has started warm enough for the market to clear the upper 70s if conditions repeat.[2]

For traders, the relevant catalysts are the day-ahead forecast, any heat advisories, and the actual airport observation around the afternoon peak. An iAlert heat advisory for western Washington on 5 August warned of highs up to 85–90°F in nearby foothill areas, indicating a broader warm spell was in play, though Sea-Tac is usually moderated by marine influence.[5] NOAA’s daily climatological reporting for SEA and the Wunderground history page are the settlement references, so any late forecast shifts, cloud cover changes, or onshore flow differences that affect the airport specifically will matter more than city-wide headlines.[16]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Sports-specific comparison page for Highest temperature in Seattle on August 5?. Polymarket's live quote (Polygon order book) plus platform attributes for the three reference venues. Sports markets reward liquidity — Polymarket and Betfair are materially deeper than Kalshi or Manifold.

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