Miami's weather has a reputation problem: mention 'marathon in Miami' and most runners picture sweltering humidity. The reality is more nuanced. Late January, when this race is held, falls in the middle of South Florida's dry season - genuinely the most comfortable window the region offers for distance running - but that doesn't mean the forecast is predictable. This guide covers the climate patterns behind race day rather than the exact averages, which are in the data card above, so you know what kind of variability to actually expect.
The dry season advantage
Miami's calendar splits fairly cleanly into a wet season and a dry one. Summer and early fall bring near-daily humidity and afternoon storms; by winter, that pattern breaks down, rainfall drops off sharply, and the near-constant tropical stickiness of summer eases into something more manageable. Late January sits close to the coolest, driest point of that cycle, which is a meaningful part of why the race is scheduled when it is - it's about as favorable as South Florida gets for a marathon-length effort.
The year-to-year swing
What the dry season doesn't guarantee is consistency from one race to the next. South Florida winters are shaped by cold fronts moving down from the north, and how often, and how strongly, those fronts arrive in any given year varies. Some editions of this race have started in genuinely crisp, ideal conditions; others have landed in a warmer stretch between fronts, with humidity building quickly once the sun comes up. Neither outcome is unusual for the race's history, which is exactly why it's worth training for a range of conditions rather than assuming the 'average' forecast is what you'll actually get.
What drives the variability
Two things matter most for how race morning actually feels. The first is timing relative to the nearest cold front - a morning shortly after a front has passed tends to be cooler and drier, while a morning in the middle of a warm stretch between fronts can feel noticeably more tropical, even in late January. The second is the sun: because the course spends long stretches on exposed causeways with no shade, conditions early in the race, before sunrise, can feel completely different from conditions two or three hours in, once the sun is up and humidity climbs with it.
How to plan around it
Because the forecast can genuinely go either way, the most useful preparation is flexible rather than specific. Pack for a wider temperature range than a single 'typical' forecast would suggest - a light layer you can discard early works for a cool start, and knowing your heat-adjusted pace works for a warm one. Check the forecast in the days immediately before the race rather than relying on seasonal averages, since a passing cold front can change conditions substantially in the final day or two. And if you want the specific coping strategies for a warm, humid morning - hydration, aid-station strategy, and pacing adjustments - this guide's companion heat-and-humidity guide for this race covers that in depth.