The 119th Boston Marathon will take place on Monday, April 20, and conditions look promising for runners set to take on the historic course.
"Right now it appears as though Monday will be a relatively cool day in Boston with temperatures no better than the 50s for highs," AccuWeather.com Meteorologist John Feerick said, adding there could be some rain during the day.
Bart Yasso, chief running officer for Runner's World, has run the marathon eight times and attended the event for 33 consecutive years.
One aspect of the ideal running conditions for the 26.2-mile-long race is moderate temperatures, typically around 52 or 53 degrees Fahrenheit for both the start and finish of the race, Yasso said.
"I always say, a little bit of cloud cover and low humidity, that would be the key," he said, adding that no wind or a slight wind is also beneficial.
One of the inherent challenges runners face on the course is the lack of shade, and if it's a bright sunny day, it can become grueling to a lot of runners, according to Yasso.
"The first time you feel shade is when you're across the finish line and you're around the tall buildings in downtown," he said.
Yasso, who is coaching 25 runners for this year's competition, said runners tend to run early in the morning or later in the day, typically avoiding the midday sun.
"That noon sun, when you get that clear day, that's when Boston can really be tough," he said
Wind also plays a key role in marathons and can either be an advantage or a disadvantage to runners, depending on the direction it blows from. If it's a windy day, marathoners must figure out which direction the wind is coming from and calculate where it will be on the course.
In 2011, a fast tailwind helped produce the fastest times ever recorded on the course, Yasso said. Geoffrey Mutai, of Kenya, finished the marathon in a record time of 2 hours, 3 minutes, 2 seconds.
Approximately 1 million spectators are expected along the streets of Boston, which is not too far removed from its snowiest winter on record. At one point, just last month, race officials were concerned what the road conditions would look like when it came time for inspections in early April.
Throughout the winter, Yasso received a plethora of questions over email and social media from snowbound New Englanders who weren't able to train outdoors and were wondering how to make up lost mileage.
Yasso advised them to avoid trying to make the miles up because injuries could occur when attempting too much mileage in a short period of time. He also recommended adjusting the goals they set for themselves.
Since the start of the marathon is broken into different waves, or groups, some entrants could see slightly different weather conditions than others throughout the day. For instance, those who have a later start time could see warmer weather during the afternoon hours.
Following the elite women's division, which begins at 9:32 a.m. EDT, the rest of the runners are situated into four waves. The first wave, which includes the elite male runners, starts at 10 a.m. with the fourth and final wave beginning around 11:15 a.m.
Boston has had its fair share of extreme weather in years past for its celebrated race. The 2007 marathon saw nor'easter conditions with driving rain and wind gusts of more than 50 mph according to Runner's World. In 1976, temperatures in the mid-90s stifled runners and in 1927, runners' shoes actually melted on an uncured road amid 84-degree heat.
What sets Boston apart from other notable distance running events is the history and tradition of the course, Yasso said. It's the oldest annual marathon and the "most prestigious finish line in running," he added.
While there have been tweaks to the starting and finish lines over time, for 118 years the course design has remained largely the same and that's "pretty special," Yasso said.
"I've run races all over the world, on all seven continents, there's just nothing like Boston. It truly is the best."