Lowest temperature in Hong Kong on July 31?

Platform comparison

Market context

Hong Kong’s low on 31 July will be set by the Hong Kong Observatory’s final **“Absolute Daily Min (deg. C)”** reading, so the trade is effectively a bet on whether the city gets a genuinely cool dawn or just an ordinary wet-season floor. July in Hong Kong is normally very warm at night, with long-run July minimums clustering around the upper 20s Celsius, which means a sub-27°C outcome is already below typical conditions and a materially lower print usually requires cloud, rain, or a tropical disturbance to suppress the overnight minimum.[1][2]

That framing helps explain why the current crowd-implied **3% YES** is so low: the market is asking for an unusually cold July day by local standards, not merely a mild one. Comparable cases show the observatory can print much lower values when heavy rain arrives; in July 2019, outer rainbands from Wipha pulled the HKO minimum down to **24.5°C** on 31 July, while July 2022 bottomed at **25.4°C** on 1 July under rainy conditions.[3][11] In a normal July regime, however, daily lows in Hong Kong sit close to 28°C, and the month’s average low is rarely far from that band.[8][4]

For traders, the immediate watchlist is the Hong Kong Observatory’s hourly readings and any late rainband or tropical-cyclone coverage affecting the territory before the daily minimum is finalised.[7][3] Because the contract settles in USDC only once the HKO publishes the relevant daily extract, there is no early cash-out from partial data: the key dependency is the final official line rather than intraday market chatter. In crypto terms, the event is small enough that broader BTC and ETH spot moves are unlikely to set the weather print directly, but sharp risk-on or risk-off flows can still matter for positioning, funding, and liquidity in the market itself if participants hedge with perps while waiting for the observatory’s release.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reads Lowest temperature in Hong Kong on July 31? on-chain. Polymarket's quote comes directly from the Polygon order book — the only comparable venue with on-chain settlement. Kalshi (USD, off-chain), Betfair (GBP/EUR, off-chain) and Manifold (play-money) are listed alongside for venue context. Every CTA routes to BTC Prediction, which mirrors the Polymarket order book directly.

Resolution & payout

Settlement is on-chain via UMA Optimistic Oracle. A proposer posts the outcome with a bond, a two-hour dispute window opens, then the smart contract lifts winning conditional tokens to 1 USDC and sends payments to holders' wallets automatically. No withdrawal fees beyond Polygon gas.

Off-chain venues (Kalshi, Betfair, Smarkets) settle in local fiat through bank-side clearing — faster than SWIFT, slower than on-chain. Manifold pays no real cash.

FAQ

What does a transaction cost on Polygon?

Polygon gas is typically under $0.01 per transaction. A full trade cycle (Approve + Order + Fill) totals around $0.03 — compared to $5-50 on Ethereum mainnet.

Can I use Bitcoin directly?

No, Polymarket operates exclusively in USDC on Polygon. You can bridge BTC to USDC via an exchange or bridge service and deposit on Polygon — typically 10-30 minutes processing time.

How does UMA secure the resolution?

The UMA Optimistic Oracle uses a bond system: a proposer posts a bond, a two-hour challenge window opens. On dispute the losing side forfeits the bond — financial incentive for honest resolution.

How volatile are crypto prediction markets?

Crypto markets react to spot prices — a 5% BTC move typically shifts a "BTC above X by date" market 10-20%. Polymarket crypto market liquidity is usually six-figure USD, sufficient for active trading.

Which crypto markets exist on Polymarket?

Currently active markets include BTC/ETH/SOL price targets, halving dates, ETF approvals, hard-fork outcomes and Layer-2 TVL thresholds. The list updates weekly; biggest volume sits on BTC and ETH price forecasts.