Miami Overnight Low June 18: Will 82-83°F Hold?

Miami’s overnight low temperature on June 18 has become one of the sharpest single-day weather markets on Polymarket. The 82-83°F bracket is trading at 72.5% implied probability, a number that jumped hard overnight as actual conditions aligned with the forecast range. The market is pricing near-certainty, not uncertainty. Here’s what the measurements are telling us.

The market question asks: what is the lowest temperature recorded in Miami on June 18? The 82-83°F outcome trades at $0.73 YES against $0.28 NO. The contract resolves at noon Eastern on June 18, 2026, against a total volume of $9,741.

How the 82-83°F Contract Works

This contract resolves YES if Miami’s official minimum temperature on June 18 falls within the 82-83°F range. The resolution source is market resolution, meaning the contract settles against the verified daily minimum reading for Miami. Eleven competing brackets cover every other plausible outcome from 73°F or below to 92°F or higher.

• YES (82-83°F) trades at $0.73, implying a 72.5% probability of resolution in this bracket.
• NO covers every other temperature bracket combined, trading at $0.28.

For this contract to pay out NO, Miami’s overnight minimum must land outside the 82-83°F range entirely. June overnight lows in Miami routinely sit in the low-to-mid 80s during peak summer humidity. The competing brackets most likely to absorb NO probability are 80-81°F and 84-85°F, but neither is trading near enough to challenge the leading bracket’s dominance.

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Momentum and Market Signals

The momentum composite here is unambiguous. The 24-hour price change of plus 21.0% combined with a trend score of 65.14 and flat 1-hour movement signals a market that surged on real-time weather data and has since stabilized at conviction. That kind of move in a short-duration contract almost always traces to actual observed conditions aligning with the forecast bracket.

Total volume sits at $9,741 with $8,043 of that arriving in the last 24 hours. Liquidity stands at $48,817, which is unusually deep for a market this size. Because total volume sits well below $1 million, a single meaningful trade can reprice this contract sharply before noon resolution. The liquidity cushion limits the worst of that volatility, but the market remains susceptible to last-hour movement.

• The 24-hour price surge of plus 21.0% connects directly to Miami overnight conditions tracking toward the 82-83°F range as June 18 began.
• The 1-hour change of plus 0.0% signals the market has reached a resting point after the overnight repricing.
• Trend score of 65.14 puts this contract in mild bullish momentum territory for the YES bracket.
• Liquidity of $48,817 against volume of $9,741 means the order book is deeper than the trading activity, reducing manipulation risk.
• Thin total volume below $1 million means a $5,000 bet in either direction would register as a significant signal.

Lines Analysis: Miami’s Summer Floor

Miami in mid-June operates under some of the most predictable overnight temperature conditions in the continental United States. Sea surface temperatures in Biscayne Bay and the adjacent Atlantic remain above 84°F through June, which acts as a thermal floor for overnight lows. The National Weather Service Miami forecast office tracks dewpoint temperatures consistently above 75°F during this period, which suppresses radiative cooling. Those physical constraints make an overnight low below 80°F essentially impossible on a normal June night without an unusual cold front, and no such front appears in the June 18 setup.

The credible NO scenario centers on the 84-85°F bracket rather than a dramatic cold break. If Miami’s overnight minimum held slightly higher than expected due to persistent onshore flow and elevated marine layer temperatures, the 82-83°F bracket misses its ceiling. That is the realistic path to a NO payout: not a cold anomaly, but a warmer-than-forecast floor. The 84-85°F bracket would need to absorb that probability, and traders appear to be discounting it heavily.

• National Weather Service Miami: any revision to the June 18 morning low observation would immediately reprice this contract before noon resolution.
• NOAA automated surface observation system at Miami International Airport: the official ASOS reading is the most likely resolution data point.
• Marine layer conditions: persistent onshore Atlantic flow pushes the overnight minimum toward the upper end of the 82-83°F range or above.
• Resolution clock: the contract resolves at noon Eastern on June 18, leaving very limited time for unexpected data revisions.

The $9,741 in total volume reflects a niche single-day weather market, not a deeply contested policy debate. The data currently favors the YES bracket. The physical climatology of Miami in June, combined with the overnight price surge, points to actual observed conditions supporting the 82-83°F outcome.

LINES VERDICT

STRONG YES LEAN

Miami’s June overnight temperature climatology and the overnight price surge to 72.5% both point to the 82-83°F bracket as the most likely resolution. The data doesn’t care about the politics, and here the data is unusually clear for a weather market.

What the market says: A 72.5% implied probability reflects strong but not certain conviction. Thin volume below $1 million means this price can shift on a single large trade before noon resolution on June 18.

Key unknown: The official NOAA ASOS reading at Miami International Airport at the time of market resolution is the single variable that settles this contract. Any late revision to that observed minimum would reprice everything.

Scientific Context

Miami’s June overnight lows have trended warmer over the past two decades. NOAA climate normals for Miami place the average June minimum near 78°F, but the updated 1991-2020 normals reflect a consistent upward shift driven by urban heat island effects and rising sea surface temperatures. The 82-83°F bracket sits above the long-term climatic average for a June overnight low, which explains why this market emerged as a credible target: June 2026 conditions appear to be running warmer than historical norms. The market is pricing a specific observed outcome, not a forecast anomaly.

What would move this price before resolution: A revised official observation from NWS Miami or an ASOS correction showing the overnight minimum came in outside the 82-83°F range would immediately reprice this contract. With resolution at noon Eastern, the window for that kind of shift is narrow.

Is the 72.5% probability meaningful?

It reflects strong trader conviction that Miami’s June 18 overnight low lands in the 82-83°F range. Prediction market probabilities are not guarantees. Thin volume below $1 million makes this price more volatile than a deep liquid market.

What pays out if this resolves NO?

Every competing bracket outside 82-83°F covers the NO side. The most plausible alternative outcomes are 80-81°F and 84-85°F. Traders buying NO are effectively betting the official minimum falls outside this specific two-degree window.

What data event would move this price most?

The official NOAA ASOS observation for Miami International Airport on June 18 is the primary data point. Any NWS Miami revision to that reading before noon resolution would reprice this contract immediately.

When does this contract resolve?

The market resolves at noon Eastern on June 18, 2026. This is an intraday contract with a hard resolution clock.

Is the volume reliable enough to trust this price?

Total volume of $9,741 is thin. Liquidity of $48,817 is deeper than the volume suggests, which limits sharp swings. But a single trade above $5,000 in either direction would register as a meaningful market signal in a contract this size.