Last year, the day before the Boston Marathon one thing appeared certain. The weather conditions were going to be almost absolutely perfect from a runner's perspective. At the time, we called them "Once in a (marathon) lifetime conditions" and LetsRun.com coaching guru John Kellogg predicted what impact the conditions would have on the performance.

Afterwards, people said a 2:03 marathon in Boston was unthinkable but it wasn't the case because one man on the planet basically predicted it - LetsRun.com's very own John Kellogg.

Well, fast forward a year and now it's the day before the 2012 Boston marathon and the law of averages has struck. Last year's weather may have been a marathoner's dream come true, but this year the weather is trying to make up for it as it's going to very hot.

As of 11:00 pm on Sunday evening, weather.com was predicting a temperature of 74 degrees at the men's start, 79 degrees one hour into the race and 81 degrees two hours in. Oh yeah, and it's going to be reasonably humid at the start - 53% at 10:00 and 39% by the end.

Editor's Update at 9:00 am on Monday: The weather.com forecast has improved by about 3 degrees for at least the first half of the race. As of now, they are predicting a temperature of 71 (not 74) at the start, 76 at 11:00 am (not 79) and 81 at 12 noon.

The only saving grace? It's may be partly cloudy and not blazing sunny.

What about the tailwind, you say? Yes, weather.com is predicting a 9 to 11 mph wind out of the SSW, but that's more of a cross tailwind than direct tailwind and John Kellogg says to be truthful the medium tailwind won't be that much of a help. On that hot of a day, runners will feel stifled if there is a tailwind, since their sweat won't evaporate as easily as if they were running into a slight (~ 5 mph) wind. Runners might actually benefit if they had a cooling breeze coming into the face and torso, which would help sweat evaporate.

So what does that mean for the winning time?

"If the winning male runs as well as the top two did last year, I'd predict the winning time would be somewhere in the mid-2:08s," said John Kellogg. "My guess is that the weather would make it roughly 3:00 slower than ideal temperatures in the 40s or 50s. It might be at least 5 minutes slower for the average runners who are out there when it's 80 degrees or above, but some of the elites are extraordinarily good in hot weather and will also finish before having to run as long in the hottest temperatures. One also needs to remember that last year's times probably got a benefit of being on the order of 2:30 faster than normal thanks to the extremely generous tailwind. So altogether for the elite men, look for the times to be about 5:30 slower than last year if they make an honest race of it and churn out similar performances."

Editor's Update at 9:00 am on Monday: With the new slightly better weather prediction, you may be wondering what that would do to John Kellogg's time prediction. So are we. The 'Rain Man' of distance running is sleeping (he generally operates on a 25 hour schedule as the mundane aspect of life is something he can't be bothered with) and so we can't get an updated prediction. Hopefully, we can keep him off a computer and ask him the minute he gets up (he won't be up most likely before the race is over). We do remember him saying 10 degrees makes a difference as he was saying that if was truly only a high of 70 in the "Duel in the Sun" then it wasn't nearly as bad as this year but this is 3 degrees (with slightly more humidity).

It's worth noting that the 2008 Olympic Beijing marathon was run with a reported starting temperature of 74 degrees, although we don't think the temperature rose all that much during the race.

The result? A winning time of 2:06:32.

How does John Kellogg explain that one?

"Either Wanjiru was one of the best hot weather runners in history or that might have been worth a sub-2:04 on a flat loop course in ideal weather. And with no rabbits and the Olympic title on the line, I still consider that to be the best marathon ever run," said Mr. Kellogg.

Screen shots with this year's and last year's Boston marathon weather forecasts appear below.

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Are you a member of the media? Would you like to speak to Mr. Kellogg? Please call the LetsRun.com offices at 607-330-4786.

More: *JK Babbles About The 2011 Boston Marathon *Official John Kellogg Is a Genius Thread (He Predicted The 2:03 On Boston) *2011: Once In A (Marathon) Lifetime Conditions Forecast For Boston On Monday

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