If you’ve been watching the Boston forecast with one eye half-closed, you can probably open it back up. Yes, a warm spell is coming to New England next week. No, it doesn’t look like it will stick around for race morning.
The latest 14-day forecast for Boston shows a sharp temperature swing in the days before the 2026 Boston Marathon. Highs are expected to reach 72°F (22°C) on both Tuesday, April 14 and Friday, April 17 — warm enough to make any marathoner nervous. But by the weekend, temperatures will drop back sharply, and race day on Monday, April 20 is currently forecast to top out at just 54°F (12°C), with a feels-like temperature closer to 45°F (7°C).
That’s close to the sweet spot most exercise physiologists and coaches consider ideal for marathon racing. According to research covered in our guide on the ideal marathon temperature, the optimal window for peak performance sits somewhere between 44°F and 59°F (7°C and 15°C).
The week before: heat, showers, and thunderstorms
The forecast between now and race weekend is messy. Monday, April 13 brings passing showers and a high of 68°F (20°C). Conditions deteriorate further by Tuesday and Wednesday, with heavy showers expected and highs in the low 70s. Thursday, April 16 carries a risk of isolated thunderstorms, before things warm up again briefly on Friday.
For runners in the final days of their taper, that’s not ideal training weather — but it’s also not the disaster scenario Boston has seen in past years. The concern with a warm pre-race week is twofold: it can tempt runners to squeeze in unnecessary last-minute miles to “feel ready,” and the body can begin adapting to warmer conditions, making a cold race morning feel jarring. Our piece on how much the heat affects your running speed explains the physiology in detail.
If you do need to run in the warmth mid-week, treat it as an easy shakeout — not a fitness test. Check out our tips for running in the heat to stay on top of pacing and hydration.
The weekend clears up — and cools down fast
By Saturday, April 18, the warm air has cleared. The high drops to 63°F (17°C), and Sunday, April 20 — the day most runners are picking up their bibs and settling into race-week routines — is forecast to be mostly sunny with a high of 54°F (12°C). A good omen.
Race day itself, April 20, is currently showing overcast skies, a high of 54°F and a low of 45°F (7°C). Winds are expected at around 11 mph (18 km/h). There is a slight chance of light sprinkles later in the day, but precipitation totals look minimal at 0.7 mm.
For context, the 2012 Boston Marathon — one of the most difficult in recent memory — saw temperatures soar to 89°F (32°C), prompting race officials to urge thousands of runners to defer. The 2018 edition sent runners through driving rain and 30 mph headwinds at 38°F (3°C). What’s on the table for 2026 looks manageable by comparison.
What runners should do with this information
The warm midweek stretch is worth watching but not worth panicking over. If you’re still running light taper workouts in the days before the race, try to do them in the cooler morning hours and avoid pushing hard in the heat. Stay well hydrated.
The bigger risk with a forecast like this is the temptation to overdress on race morning because the previous week felt warm. With a feels-like temperature of 45°F at the start, you’ll want layers at the start line — but plan to shed them early. Check your race day checklist and make sure you’ve packed some throwaway layers for Hopkinton. Most races collect and donate discarded clothing, so you won’t be leaving anything to waste.
For a full breakdown of what to wear at different temperatures, our guide to the best temperature for running has you covered.
Keep an eye on updates closer to race day. Forecasts at 12 days out carry significant uncertainty, and Boston’s weather has a long history of surprising even the most prepared runners. We’ll update this forecast as Marathon Monday gets closer.
Weather data sourced from timeanddate.com, April 9, 2026.
