Lowest temperature in Hong Kong on August 5?

Platform comparison

Market context

Hong Kong’s lowest temperature on 5 August will be set by the Hong Kong Observatory’s final daily minimum reading in Celsius, reported to one decimal place, and the market will resolve only once that daily extract is published. Polymarket is currently pricing the event with a crowd-implied probability of 0% for YES on the title as phrased, while its own event page shows the active temperature outcomes clustered around 26°C and 27°C, which underlines how these contracts are quoted as outcome prices rather than traditional decimal odds. By contrast, Kalshi-style books typically surface prices as cents-per-contract, while Betfair and Smarkets display exchange-style prices with commission layered on afterwards, so the same weather view can look materially different across venues because of fees, liquidity, and account access.

The closest comparables suggest this is usually an overnight-minimum trade rather than a daytime-heat trade. Polymarket’s event commentary points to forecast lows of 26–27°C under cloudy skies with scattered thunderstorms tied to a broad monsoon trough, and the Hong Kong Observatory’s regional readings page keeps Hong Kong firmly in humid summer conditions. A recent public weather bulletin for 5 August also placed the city in a hot, rainy pattern, consistent with lows staying in the mid-to-high 20s rather than dropping sharply. August 2025 offers a useful analogue: the Observatory recorded a month-low of 24.0°C on the morning of 5 August, showing that unusually wet setups can still pull minima down, although that outcome is less common than a warm, muggy floor.

For traders, the main catalysts are the Observatory’s overnight forecast updates, any thunderstorm or rainband revisions, and the timing of the final “Daily Extract”, because the settlement source explicitly ignores later corrections once initial publication is made. That makes the key dependency not just the observed temperature, but whether the Observatory publishes an absolute daily minimum that lands in a neighbouring bracket such as 26.0°C, 26.5°C or 27.0°C. On platforms with tighter spreads and lower fees, late moves can be more sensitive to a single forecast update; on exchange books, the same information can move more slowly if liquidity is thin or KYC access is narrower.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page compares Lowest temperature in Hong Kong on August 5? 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 UK, 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.

UK Frequently Asked Questions

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.

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.

Polymarket vs Betfair Exchange: which is better for UK prediction trading?

Betfair Exchange offers UKGC regulation, GBP settlement, and potentially tax-free winnings — but focuses on sports and politics only. Polymarket has deeper liquidity, 0% platform fee, global event coverage, and crypto/geopolitical markets Betfair doesn't offer. For UK traders: Betfair for regulated GBP sports markets; Polymarket for broader, global prediction events.

Is Kalshi available in the UK?

Kalshi is a US CFTC-regulated prediction exchange. UK residents can create accounts but must use USD and US payment methods. Kalshi's product range overlaps with Polymarket but with lower liquidity on most contracts. For UK traders, Polymarket typically offers better prices due to higher global volume.