Boston Marathon runners will withstand a bit of rain and a headwind this year

April weather in Boston can range from scorching hot to bitterly cold,
with everything in between. It's no wonder that those hoping to run or watch the Boston Marathon often watch the forecast closely in the days leading up to the historic race.

Perfect Boston Marathon weather for runners would be temperatures around 45 to 50, overcast skies, with a west or southwest breeze, essentially a tailwind, and just enough moisture in the air to minimize the risk of dehydration. Occasionally, the forecast on Patriots' Day brings ideal conditions for the race, but that good fortune comes infrequently. This year is no exception.

Areas of low clouds and patchy fog this morning may yield a few patches of light drizzle or an isolated shower prior to the beginning of the race. Temperatures will be right around 50 degrees as the elite runners take off. The highs will rise to the mid-50s as the additional waves of runners leave Hopkinton.

There won't be much change in the temperature along the route or throughout the day. You can expect highs to top out just shy of 60 degrees away from the coast, and in the mid-50s in the city.

The elite runners literally will be racing against advancing showers, and they'll likely lose that contest. A round of scattered showers is anticipated to move in along the course route between 10 a.m. and noon.

The big concern, of course, with wet weather will be that any raindrops take away from body heat and make the roads a bit slick. While we mostly hear about hypothermia affecting humans in very cold temperatures, it can happen at cool or even warm temperatures if you're too chilled from sweat or rain.

Those that run at a slower pace do not generate as much internal metabolic heat as faster runners, so adding some wetness like a bit of rain increases the likelihood for hypothermia.

In terms of wind, runners will have to contend with a headwind or quartering headwind along the entire race route.

Wind speeds won't be overly impressive. However, a steady 10-15 mph breeze, including a few gusts up to 20 mph in the late afternoon to early evening, could slow some runners down over the 26.2-mile course.

The good news for both runners and spectators alike is the rain is not supposed to last the entire day. In fact, there should be some random lulls and breaks in the action throughout the marathon. The back edge of the showers should arrive in the city between 3 p.m. and 5 p.m. Skies will be overcast the entire day until some partial clearing occurs in the evening.

The bottom line? Runners will be forced to dodge some raindrops and struggle against a headwind. Spectators would be smart to keep warm and bring along a raincoat, poncho or umbrella.