Miami Overnight Low on May 28: Can 78-79°F Hold?

Miami’s overnight low temperature on May 28 is a tighter call than the calendar suggests. Late May in South Florida sits in that shoulder season where tropical moisture and sea surface temperatures keep nighttime lows stubbornly warm, but synoptic-scale wind shifts can still pull numbers a degree or two in either direction. The 78-79°F bracket carries a 41% implied probability right now, and the market has been moving hard toward it in the last 24 hours.

The market question asks for the lowest temperature recorded in Miami on May 28. The 78-79°F bracket is priced at $0.41 YES and $0.59 NO. The market resolves on May 28 at 12:00 UTC. Total volume stands at $5,360, with $2,582 traded in the last 24 hours.

How the 78-79°F Contract Works

Resolution means the official overnight low temperature recorded in Miami on May 28 falls within the 78-79°F range. The market resolves YES if the measurement lands at 78°F or 79°F. The resolution source is the market itself, drawing on official meteorological observation.

• YES ($0.41, 41% probability): Miami’s overnight low on May 28 measures 78°F or 79°F.
• NO ($0.59, 59% probability): Miami’s overnight low on May 28 falls in any other bracket, including 80-81°F, 76-77°F, or beyond.

The NO side wins when the overnight low misses the 78-79°F window entirely. Late May Miami averages overnight lows in the low-to-mid 70s historically, but sea surface temperatures in Biscayne Bay and the Atlantic have been running above average in 2026, pushing marine influence higher. A persistent onshore flow or elevated dewpoints can anchor lows near 80°F or above. A brief dip in winds or a dry air intrusion could push the low toward 76-77°F. Either scenario pays out NO.

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Momentum and Market Signals

The momentum composite here is a strong directional signal. The 78-79°F bracket gained 14% in the last hour and 15.5% over 24 hours, with a trend score of 63.97. That kind of movement in a one-day weather market almost always traces back to updated model output, specifically the 00Z or 06Z GFS and Euro runs refreshing overnight low guidance for Miami. Traders are repricing based on what the models are now showing for Wednesday morning.

Total volume is $5,360 with $2,582 in the last 24 hours and $9,055 in liquidity. This is a thin market. Volume well below $1M means a single mid-sized bet can move this price sharply. The momentum signal is real, but treat the magnitude with some caution. Thin liquidity amplifies price swings in both directions.

Key Factors:

• The 78-79°F bracket jumped 14% in the last hour and 15.5% over 24 hours, driven by updated short-range model guidance for Miami’s overnight low.
• Late May Miami sees overnight lows heavily influenced by Atlantic sea surface temperatures, which are running above the long-term average in 2026.
• The competing 80-81°F bracket is the primary alternative, reflecting the possibility that marine warmth keeps the low elevated above 79°F.
• The 76-77°F bracket represents a cooler scenario requiring a wind shift or reduced dewpoint, currently less favored by market pricing.
• With less than 24 hours to resolution, any final model run showing a clear overnight low consensus would likely push this bracket toward 50% or away from it quickly.

Lines Analysis: What the Miami Data Is Saying

Here’s what the measurements are telling us. Miami’s proximity to warm Atlantic waters in late May creates a narrow band of likely overnight lows. The 78-79°F bracket sits right at the median of what current atmospheric conditions support. Above-average sea surface temperatures in 2026 bias the distribution slightly warmer, which is why 80-81°F remains a credible competing bracket. The sharp momentum toward 78-79°F over the last 24 hours suggests short-range models have converged on that range as the most likely outcome for Wednesday morning.

The 80-81°F bracket is the real threat to the YES side here. A persistent southeasterly flow off the warm Atlantic, combined with elevated boundary layer moisture, could keep the minimum temperature from dropping below 80°F. That scenario does not require anything unusual for late May Miami. The data doesn’t care about the politics of what bracket you hold.

Signals to Monitor:

• The 06Z and 12Z GFS and European model runs for Tuesday evening will show the clearest guidance on Miami’s overnight minimum temperature for May 28.
• National Weather Service Miami Area Forecast Discussion updates will flag any surface boundary or wind shift that could move the low outside the 78-79°F window.
• Current sea surface temperatures in Biscayne Bay and coastal Atlantic waters are a structural warm floor for overnight lows in late May.
• A sudden increase in volume or price movement on the 80-81°F bracket would signal traders repricing toward a warmer overnight scenario.
• Any observed temperature data from the early morning hours of May 28 would rapidly collapse uncertainty in this market.

The market is pricing uncertainty, not science. Total volume of $5,360 reflects that this is a small, short-duration weather market with modest conviction. The data from updated model runs clearly moved the 78-79°F bracket higher in the last 24 hours. Whether that model signal holds through Wednesday morning is the only remaining question. The current 41% probability reflects a real but not dominant chance that this specific two-degree window captures the official overnight low.

LINES VERDICT

Narrow Window, Real Chance

The 78-79°F bracket has momentum and meteorological logic behind it, sitting right at the central tendency of late May Miami overnight conditions given current Atlantic sea surface temperatures and model guidance.

What the market says: A 41% implied probability means the market sees this as the single most likely outcome but does not consider it a lock. Thin liquidity means the price could shift significantly on any final model update or early observed temperature data before the May 28 resolution.

Key unknown: The final 12Z NWS Miami forecast and any early morning temperature observations on May 28 are the only data that will definitively resolve where the overnight low lands relative to the 78-79°F bracket.