The 121st running of the Boston Marathon will take place with generally great weather for both runners and spectators.  It won’t be cold and damp nor will it be hot and humid, both of which have happened in the past.  

This year runners and spectators have some weather to be happy about.  Let’s start with the spectators.  If you are watching the marathon you don’t want it to be too hot, too cold or wet.  This year, after a very warm Easter the day before, cooler air from Canada will arrive in time for the marathon.  If you are getting up early to help a runner to the race, expect temperatures in the upper 50s, not too chilly even at sunrise.

From about 10 a.m. until 5 p.m. temperatures will range from 60 to 66 degrees, not a wide range and not very warm.  Imagine watching the first half of the race back in 1976 when it was in the 90s or standing along the route in the 50 degree weather and  torrential rain which occurred in 2007.  There were even snow squalls 50 years ago, 1967.

While this year temperatures will be comfortable, it will also be mostly sunny.  Use sunscreen throughout your time outside.  The sun is very powerful in mid-April, more than you realize. It’s basically the same as late August.

For runners, your initial reaction might be that temperatures in the 60s are too warm for a marathon. While that’s probably true, the relative humidity is going to be very low.  This is important because it will help wick the sweat off your body and cool you down.  This also mean water loss will be high so be sure to take advantage of those water stations.  

Low humidity will help the runners stay cool in spite of temperatures in the 60s. Dave Epstein

Winds are going to be favorable for runners this year. I expect we might even see a record or two fall because of the northwest wind.  The wind direction isn’t exactly perfect, but it’s pretty close.  This time of year there’s often a head wind for runners as they pass Newton and head into Boston but this year the wind will be at the back of the participants the entire way.  The wind will be consistent and help will help runners get to the finish line.

Look for sunshine along the entire marathon route this year. Dave Epstein

Of course the same weather runners and spectators will experience on the course of the marathon will also be enjoyed by baseball fans at Fenway park during the traditional Patriot’s Day game. Other celebrations taking place during the day can count on cooperation from Mother Nature as well.

Follow Dave Epstein’s forecast on Twitter @growingwisdom