Miami Lowest Temp May 20: Can 76-77°F Hold?

Miami’s overnight lows in mid-to-late May rarely surprise. The Atlantic sea surface temperatures that buffer the city against cold snaps are at their warmest of the year, and the synoptic pattern heading into May 20 shows no cold front capable of pushing the thermometer below 74°F. The question here is not whether Miami will be cold. The question is which narrow two-degree band the overnight minimum lands in, and whether the 76-77°F bucket is the right one to hold.

The market has priced the 76-77°F outcome at 24%, with the implied probability sitting flat for the last 24 hours. This is a multi-outcome market, so 24% is actually a meaningful signal. Among roughly a dozen two-degree buckets spanning the possible range, one outcome capturing nearly a quarter of the probability mass suggests real trader conviction. But at $1,194 in total volume, this market is thin. A single large bet can reprice any outcome sharply before the May 20, 2026 12:00:00 resolution.

How the 76-77°F Contract Works

The contract pays out if the verified lowest temperature recorded in Miami on May 20, 2026 falls between 76°F and 77°F inclusive. Resolution follows the official weather measurement for Miami, per Polymarket’s stated source. The contract closes at 12:00:00 on May 20, 2026.

• 76-77°F (YES): $0.24 per share, implying 24% probability.
• All other outcomes (NO): $0.76 per share, implying 76% probability spread across all competing buckets.

The competing outcomes are not equally likely. The 74-75°F bucket and the 78-79°F bucket are the next-closest alternatives. Miami’s May overnight lows cluster between 72°F and 80°F historically, with the modal value sitting in the mid-to-upper 70s. A reading above 80°F is possible but would require unusually persistent warm advection overnight. A reading below 74°F would require a front that current models are not showing. The 76-77°F range misses when the overnight low drifts one bracket warmer into 78-79°F territory, which is the single most likely alternative given the current atmospheric setup.

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Momentum and Market Signals

The momentum composite for this contract is flat. The 1-hour and 24-hour price changes both read zero, and the trend score of 24.58 reflects a market in a holding pattern rather than one responding to new information. The most natural driver for movement here is an updated National Weather Service forecast for Miami on May 19 or early May 20, which would give traders a tighter range before resolution.

Total volume stands at $1,194, with $369 traded in the last 24 hours. Liquidity sits at $10,187, which means the order book has depth relative to what has traded. At this volume level, the price is more a reflection of passive order placement than active trading conviction. A single informed bet of a few hundred dollars can move this contract meaningfully. Treat the 24% price as directional, not precise.

• 1h and 24h change both at zero: No new weather data or forecast update has moved traders since yesterday, indicating the market is waiting on the National Weather Service’s evening forecast package for South Florida.
• Trend score of 24.58: This reflects low but nonzero activity, consistent with a market that attracted initial interest and has since gone quiet ahead of resolution.
• Total volume below $1M: Thin liquidity means any new meteorological signal, an updated high-resolution model run or a National Weather Service special weather statement, could shift the price sharply within minutes.
• The 78-79°F bucket is the primary competing outcome: If Miami’s sea breeze weakens or a warm air mass sits overhead longer than expected overnight, capital would rotate toward the warmer buckets.
• No whale activity recorded: The absence of large individual bets means no single trader has taken a strong directional position, consistent with genuine uncertainty about the specific two-degree landing zone.

Lines Analysis: Where the Data Points

The National Weather Service’s climatological record for Miami in late May places the average overnight low around 75-77°F. The 76-77°F bucket sits squarely in the climatological sweet spot for this date. That alignment is the primary reason 24% is a defensible price. If you forced a single bucket to carry the most probability weight based on climate normals alone, this one has a reasonable claim. Here’s what the measurements are telling us: the base rate for this outcome is not far from what the market is already pricing.

The case for the contract missing is straightforward. Miami’s overnight lows on any given May night are genuinely uncertain within a five-degree window. The 78-79°F bucket benefits from the same warm-bias that makes late May lows run slightly above the long-term average in recent years. Sea surface temperatures in Biscayne Bay and the nearby Atlantic have trended higher over the past decade. That warm bias nudges the probability distribution toward the warmer buckets and away from 76-77°F. A low that settles at 78°F or 79°F would resolve this contract worthless despite being only one to two degrees warmer than the target.

• National Weather Service Miami Area Forecast Discussion: any overnight low forecast update narrowing the range below 77°F or above 77°F will reprice this contract before resolution.
• High-resolution model consensus (NAM, HRRR): agreement among short-range models on an overnight minimum in the 76-77°F band would support the current 24% price.
• Sea surface temperature anomalies in the Florida Straits: persistent warm anomalies elevate the probability of warmer buckets taking the resolution.
• Synoptic setup on May 19 evening: any cold front passage, even a weak one, would shift probability toward the 74-75°F bucket and away from 76-77°F.
• Convective activity overnight: thunderstorm outflow boundaries can briefly drop Miami temperatures by two to four degrees, creating a temporary spike toward lower buckets before the low is officially recorded.

At $1,194 in total volume, the market is not deep enough to treat the 24% price as a precise calibration. The data favors this outcome as a legitimate contender, but the thin order book means the price reflects a small number of traders’ best guesses rather than aggregated information. The 76-77°F outcome has a fair claim on roughly one-in-four odds, but the warm-skewed climatology of modern Miami keeps the competing buckets well within reach.

LINES VERDICT

Legitimate Contender, Fragile Lead

The 76-77°F bucket sits in Miami’s climatological comfort zone for late May, but the warm bias in recent years makes the 78-79°F outcome a persistent rival. The data doesn’t care about the politics of any particular forecast, and right now the data is genuinely ambiguous within this narrow range.

What the market says: At 24%, traders are giving this outcome roughly one-in-four odds. That is a modest but real signal of conviction in a multi-bucket market. With resolution at 12:00:00 on May 20, 2026 and thin volume, the price can shift sharply on any National Weather Service forecast update tonight.

Key unknown: The National Weather Service’s final overnight low forecast for Miami on May 19, combined with updated high-resolution model guidance, is the single data point that would most likely reprice this contract before resolution.

FAQ

• What does 24% probability mean here? In a multi-outcome market with roughly a dozen buckets, 24% means traders believe this specific two-degree range is the single most likely or near-most-likely landing zone for Miami’s overnight low on May 20.
• What happens if the overnight low lands in a different range? The 76-77°F contract pays zero. Every other bucket is a separate contract, and capital would flow to whichever bucket captures the actual recorded minimum.
• What single event would most move this contract’s price? A National Weather Service forecast update on May 19 evening that explicitly calls for an overnight low of 76°F or 77°F would push this contract toward 40-50%. A forecast of 78°F or above would deflate it.
• When does this contract resolve? Resolution is set for 12:00:00 on May 20, 2026, based on the official lowest temperature recorded for Miami on that date.
• Is the volume reliable enough to trust the price? At $1,194 total volume, reliability is limited. The order book has $10,187 in liquidity, but the small amount actually traded means a single new bet can shift the quoted probability by several percentage points.

This analysis reflects market conditions as of 2026-05-19 06:42:43. Prediction market probabilities are volatile and shift as new data and regulatory decisions emerge, especially as the 2026-05-20 12:00:00 resolution date approaches. Lines.com does not accept bets or provide financial or gambling advice. All market outcomes are uncertain.