Boston Marathon Weather History: What 20 Years of April Data Reveals

April in Boston is a coin flip with consequences. The same 26.2-mile stretch from Hopkinton to Copley Square has seen 89°F heat emergencies, 30 mph headwinds with driving rain, and pristine 50°F tailwind days that produced the fastest times in marathon history. Your race plan needs a weather contingency, and the historical record explains why.

Over the last two decades, race-day highs have swung by nearly 50 degrees. The average finish-line temperature sits around 59°F, but averages are misleading when individual years range from freezing rain to sunburn. Here is what April has actually delivered, year by year.

The Numbers: 20 Years of Boston Marathon Weather

This table covers race-day conditions from 2004 through 2025. Start temperatures reflect Hopkinton readings near gun time; highs are measured along the course. Wind and precipitation are approximate course-wide conditions.

* 2020 was cancelled due to COVID-19. 2021 was moved from April to October.

Why Wind Matters More Than Temperature

Boston is a point-to-point course running west to east from Hopkinton to Copley Square. That geometry turns wind direction into the single biggest performance variable on race day. An easterly wind means a headwind for all 26.2 miles. There is no shelter, no turnaround, no course section running the other direction to balance things out.

Wind is also asymmetric in its effect on runners. Even a modest 5 mph headwind can add 10-15 seconds per mile. A 5 mph tailwind only saves 3-5 seconds. At stronger winds, the penalty grows exponentially — a 15 mph headwind can cost 30-60 seconds per mile depending on pace. Over a full marathon, headwind years routinely add 5-20 minutes to finish times, while tailwind years save far less. The course punishes bad wind days far more than it rewards good ones.

April is Boston's windiest month, averaging about 14 mph with a 55% chance of sustained winds above 13 mph on race day. The prevailing April wind direction tends slightly south of east, which means a mild headwind is actually more common than a tailwind. When a strong easterly system sets up, as it did in 2018 and 2007, the course becomes a 26-mile wind tunnel.

Wind also disproportionately affects faster runners. The aerodynamic drag of running into a 10 mph headwind at 5:40/mile pace is roughly double the drag at 8:00/mile pace. Elite and sub-elite runners lose more time per mile in headwind conditions than mid-pack runners do.

The Worst Weather Years

2018: The Headwind Deluge

The 2018 Boston Marathon stands as the most brutal weather day in modern race history. Wave 1 crossed the start line in Hopkinton at 38°F with a wind chill of 29°F, running into sustained 25–30 mph easterly headwinds with gusts reaching 45 mph. Heavy, driving rain fell for the entire race. Reports of sleet at the start line circulated that morning.

The combination was devastating. Average finishing times across all ability levels slowed by 15–20 minutes. Nearly 4,000 runners dropped out, roughly double the normal attrition rate. Medical tents treated 2,785 runners, with the vast majority presenting hypothermia symptoms rather than the dehydration typical of warm years. Desiree Linden won the women's race in 2:39:54, ending a 33-year American drought, while Japan's Yuki Kawauchi surged past fading competitors to win the men's race in 2:15:58.

2012: The Heat Emergency

The 2012 race delivered the opposite extreme. Start temperatures in Hopkinton hit 72°F and climbed to 89°F along the course by early afternoon. The B.A.A. took the unusual step of offering all registered runners a deferral to 2013. About 14% of entrants did not pick up their bibs.

Among those who started, more than 2,100 received medical treatment for dehydration and heat exhaustion. Multiple runners arrived at medical with dangerously elevated core temperatures. The B.A.A. nearly doubled water supplies at every station. Wesley Korir won in 2:12:40, significantly slower than recent years. Defending champion Geoffrey Mutai, who had run 2:03:02 the year before, dropped out at mile 19 with cramps.

2007: The Nor'easter

A late-season nor'easter parked south of Boston on race day, bringing heavy rain that mixed with sleet and easterly wind gusts above 35 mph. Robert Cheruiyot defended his title in 2:14:13, more than seven minutes slower than his course record from the previous year. It was the slowest winning time in 30 years.

2004: The Forgotten Heat Wave

Before 2012 became the benchmark for hot Bostons, 2004 held that distinction. Temperatures reached 86°F at the finish, the hottest race day since 1976. Roughly 4,000 registered runners either did not start or did not finish. Medical tent volumes spiked to nearly 10% of the field.

The Best Weather Years

2011: The Tailwind Marathon

The 2011 Boston Marathon produced conditions that marathon runners dream about. Temperatures sat in the high 40s to low 50s under sunny skies, and a 15–20 mph southwesterly tailwind pushed runners east toward Boston for the entire course. Expert analysis before the race estimated the tailwind alone was worth 3–4 minutes for elite runners.

Geoffrey Mutai ran 2:03:02, the fastest marathon time ever recorded at that point, though it was not ratifiable as a world record due to Boston's elevation drop and point-to-point course. Ryan Hall finished in 2:04:58, the fastest marathon ever by an American runner at the time. The conditions demonstrated exactly how much a sustained tailwind can do on this specific course geometry.

2025: Near-Perfect Cool

The 2025 edition delivered textbook racing weather. Temperatures started in the high 40s in Hopkinton and peaked near 60°F, with dry air at 52% humidity and a dew point of just 35°F. A light south-southeast crosswind was the only blemish. Sharon Lokedi set a new women's course record at 2:17:22, and John Korir won the men's race in 2:04:45, the second-fastest time in course history.

2022: Sunny and Cool

Race day brought 54°F and sunny skies with minimal wind. It was a straightforward, no-excuses day that rewarded fitness and smart pacing. Many runners logged personal bests.

2010: Calm and Crisp

Temperatures in the upper 40s with little wind and dry skies. Cool enough to keep the body from overheating, warm enough to avoid layers. The kind of day where your training, not the weather, determines the outcome.

How to Prepare for Anything

Check the forecast 48 hours out, then again race morning. The 10-day forecast for Boston in April is notoriously unreliable. Two days out gives you enough accuracy to commit to a gear plan and pacing strategy.

Prepare two gear plans. Lay out a warm-weather kit (singlet, visor, extra electrolytes) and a cold-weather kit (arm sleeves, light gloves, vest) the night before. Decide in the morning when you step outside. Boston has surprised enough runners that going in with a single plan is a risk.

Dress for Hopkinton, not Boston. The start village sits at 490 feet elevation and is routinely 5–10°F colder than downtown Boston at the finish. Bring throwaway layers for the Athletes' Village wait. You will warm up as you descend toward the coast.

Know the wind direction before you set your goal. If the forecast shows easterly winds above 10 mph, add 30–60 seconds per mile to your realistic goal pace. Trying to fight a headwind at goal pace for 26.2 miles is how you blow up at Newton. In 2018, runners who adjusted early finished; those who tried to push through the wind dropped out.

If it is warm, run effort from the gun. The 2012 and 2004 races proved that heat at Boston is a medical emergency waiting to happen. Pre-load electrolytes, wear sun protection (the course runs east and afternoon sun hits your back from miles 16–26), and accept a slower time rather than chasing a number that the conditions will not allow.

Later waves face worse conditions. With six waves in 2026, the last wave starts over an hour after the first. Temperature, sun exposure, and wind can all change meaningfully in that window. If you are in Wave 5 or 6, plan for warmer conditions than the morning forecast suggests.

More Boston Marathon Guides

• Boston Marathon Course Strategy — Mile-by-mile breakdown from Hopkinton to Boylston.
• Boston Marathon Qualifying Guide — BQ standards, registration, and cutoff history.
• Boston Marathon Packing List — What to pack for every weather scenario.
• Running a Hot Marathon — Pacing and hydration adjustments when race day turns warm.
• Boston Marathon Weather Forecast — Live conditions, weather-adjusted pacing, and course analysis.