BU Marathoncast - Boston & London

 

Meet Connor Lewis! Boulder Underground athlete coached by Matt Hensley AND our Race Meteorologist.


Connor has been a distance runner since he graduated college and happens to be a meteorologist! He was a broadcast meteorologist for seven years and now works for the National Ocean Service. Whether you’re traveling to the race or watching at home, we all know how valuable a forecast can be, so Connor is here to provide guidance on some of the year’s biggest races from a runner’s perspective. 


Upcoming Forecasts

  • Boston Marathon

  • London Marathon

 
 

The London Marathon


Sunday April 26th, 2026


Spring is the driest part of the year in London. Their wettest months are August through January, so it makes sense for the Brits to host their marathon in April. 


London’s latitude is equivalent to Calgary, Alberta, but the radiation from the sun might be stronger than you think this time of the year. It’s enough to put sunscreen on, that’s for sure! The table below shows the solar flux at noon for the Boston, London, and New York City Marathons. The spring sun can be sneaky!

 
 

London Climatology on April 26th

  • Avg. High: 61

  • Avg. Low: 46

  • Avg. Precipitation: 0.14”

  • Record High: 85

Similar to the Pacific Northwest, the UK’s weather is dictated by the ocean and relatively predictable. We shouldn’t expect too many surprises with a forecast in London. 

Sunday Start Times:

  • 8:50 AM: Elite Wheelchair Races (Men and Women)

  • 9:05 AM: Elite Women’s Race

  • 9:35 AM: Elite Men’s Race

  • 9:35 AM – 11:30 AM: Mass Participation Start

    • The mass start is organized into dozens of waves. The fastest runners (sub-2:30) go off with the elite men at 9:35 AM, while the final waves set off until 11:30 AM.

London Marathoncast:

Starting line: 50 degrees, mostly cloudy, calm winds, 0% chance of rain

Finish line: 63 degrees, mostly cloudy, calm winds, 0% chance of rain

With a late-ish start time, the weather will be noticeably warmer at the finish line. We’ll give the temps a B-, so the cloud cover and humidity will be major factors on race day performance. Easily the best part of the forecast is the unusually dry air! Dew points will start in the 40s and drop into the 30s by the end of the race. As far as London standards, Saturday morning will be bone dry, and Sunday’s dew points won’t bother you too much. 

There will be a blanket of thin, high clouds. Whether low-light or normal, I’d wear some sunglasses. You’ll be squinting without them. These won’t be dense rain clouds, but it’ll take an edge off the warmth. If anything, it’ll get slightly cloudier as the day progresses. 

The rest of the forecast is very straightforward. The winds should be light and imperceptible. There is no chance of rain. Patchy fog is possible around sunrise. 

Overall, it could be better, could be worse! There will be some fast times, but I think the course record is safe. Best of luck to those lucky enough to run this race!

 

130th Boston Marathon




Monday April 20th, 2026




Growing up in Southeast Massachusetts, I can tell you that the “April showers bring May flowers” proverb holds very true in Boston. Red Sox games were always a little cheaper in April, because the weather is…iffy! My dad’s birthday is on April 12th. Picture a man from Brockton with a Ben Affleck-style accent lamenting that his birthday wasn’t in the summer. But my dad is a talented landscaper, not a runner. The Boston Marathon is in mid-April, because it has the best weather, on average, for a 26.2-mile run without the risk of snow or a nor’easter. Unlike other majors, I think the Boston Marathon takes place during the most ideal week of the year. With that being said, thunderstorms, torrential rain, freezing wind chills, graupel, and heat/humidity are all on the table. While the average temperatures look perfect, Boston’s weather in April is inconsistent and frankly unpredictable. 




Take a moment to consider that you’re starting inland at 470 feet above sea level and running 26 miles east to the coast. It’ll probably be colder in Hopkinton than Boston in the morning. For this race, I really try to understand how the weather will change from the start to finish line.




Climatology on April 20th




  • Boston Logan International Airport

    • Avg. High: 58

    • Avg. Low: 43

    • Avg. Precipitation: 0.11”

    • Record High: 89

    • Record Low: 34




  • Worcester Regional Airport (~15 miles west of Hopkinton)

    • Avg. High: 58

    • Avg. Low: 38

    • Avg. Precipitation: 0.13”

    • Record High: 83

    • Record Low: 27




Understanding Boston’s climate and this year’s forecast is crucial to having a fun day. Let’s start with the mid-April sun angle that is equivalent to the sun angle in mid-August! There’s probably a logistical reason, but I often wonder why the race doesn’t start an hour earlier due to this factor. Unless the forecast is completely overcast, you MUST consider the extra warming effect of the strong sun on your skin, and yep, wear sunscreen. If the temperature is 50 degrees at noon with light winds, the real-feel temperature is actually 55. On the flip side, the starting temperature for my first Boston Marathon in 2022 was 34 with zero wind and clouds, so I was very comfortable in my normal shorts, singlet, and throwaway hat/gloves. For marathoners in later waves and running 4+ hours, you will spend more time running when the sun is at its strongest, therefore, the cloud coverage is even more important. To further convolute things, the dew point can range from the teens to the 60s. 




When you look back on past races, half the time the weather cooperates, half the time it doesn’t. Personally, this checks out. My other Boston Marathon in 2023 featured thunderstorms for the final 5k and left me soaked and shivering while I waited for my gear bag. Yin and yang, I suppose!




  • “Best” weather of all time

    • 2011 Boston Marathon: Temps near 50, sunny, WNW wind at 20 mph. Persistent tailwind results in a 3-minute course record for men. Remains the men’s course record to this day: 2:03:02 – Geoffrey Mutai (KEN).

       

  • “Worst” weather of all time

    • 1976 Boston Marathon: Record highs, parts of the course reach 90 degrees.

    • 2018 Boston Marathon: Temps in the 40s, torrential rain, NE wind at 20 mph, numerous athletes hospitalized for hypothermia.




I love this race for so many reasons. Besides an epic course and crowd, Patriots’ Day is a celebration like none other. I hope this background information and forecast helps you make a confident and realistic race strategy.



Forecast Updated 4.11.26 at 4 PM MT



Boston Marathoncast: 30% chance of rain, partly sunny, breezy, temps near average



Hot weather is on the way to Boston this week. Good news – it can’t last forever, especially this time of the year. The extended period of warmth will snap with a cold front right around Marathon Monday. The big question is when exactly does this front reach Boston. 



As of now, Sunday looks warm, and Monday looks active. Then Tuesday would be perfect running weather. Let’s hope the weather pattern speeds up a bit and the cooler weather settles in well before the start of the race. At this point, I’m not too concerned about excessive warmth for the marathon. It might be smart to do some last minute running with arm sleeves or other go-to cold running gear. 



The forecast will change, so take these models with a grain of salt. It is interesting to see the Euro spit out some mixed precipitation in the Berkshires (Western Mass)! 



You might need to stuff the suitcase with clothes for cold and warm weather. Classic New England!

 
 

Updated 4.13.26 at 9 AM MT

Starting line: 30% chance of rain, mostly cloudy, temps in the upper 30s, wind chills near 30, windy.

Finish line: 20% chance of rain, decreasing clouds, temps in the upper 40s, wind chills near 40, breezy.

Forecasting in New England 3+ days into the future is a challenge, so my first piece of advice is don’t let your iPhone weather app dictate your anxiety levels. All I can say with confidence is that warm weather does not look likely for Marathon Monday. I expect temperatures to be near or below average, which is great news! It might be wise to do some last minute practicing with arm sleeves or other cold running gear, since wind and/or rain continues to seem like a factor. 

If there was ever a race to buy some comfy, warm throwaway clothes, it’s this one. You will be spending a lot of time outside in the athlete village waiting for your wave, and you’ll be miserable if you don’t have adequate throwaway clothes. Not quite as luxurious as the elite tent spacewarmer, a garbage bag could be a lifesaver if you need a wind or rainproof layer in the village! 

If you’re flying to Boston soon, I’d bring all your favorite wind and rain gear. I’d have an outfit for subfreezing wind chills or cold rain, just in case. The race requires your bib to be visible at all times on the course, so keep that in mind with any potential gear combos.

So far so good, but remember, the forecast WILL change!

 
 
 

Division/Category - Start Time

  • Wheelchair Men - 9:06 a.m.

  • Wheelchair Women - 9:09 a.m.

  • Handcycles/Duos - 9:30 a.m.

  • Professional Men - 9:37 a.m.

  • Professional Women - 9:47 a.m.

  • Para Athletics Division - 9:50 a.m.

  • Wave 1 - 10:00 a.m.

  • Wave 2 - 10:15 a.m.

  • Wave 3 - 10:28 a.m.

  • Wave 4 - 10:41 a.m.

  • Wave 5 - 11:01 a.m.

  • Wave 6 - 11:21 a.m.

 
 

Photos by: Tracy Ann Roeser/ Tracy Ann Creative

Matt Hensley