I should start by stating the obvious: this isn’t really urban planning-related post. Except that shutting down a major city for a road race kind of is urban planning. And busing 30,000 people certainly is. But I’m not going to focus on that.

Some of you may know that I run marathons from time to time. Some of you may even know that I had an infamous run-in with the heat in Boston a few years ago. I have a number for this spring, and I’ve even been attempting to do some training. But with COVID-19, the whole operation appears to be grinding to a halt: the B.A.A. is planning to postpone the race to the fall, and they are rumored to be looking at dates in mid-September, when the average high temperature is in the mid-70s and one in five days eclipses 80.

Here’s my two cents on that: It’s a Bad Idea. Not the postponement: that’s probably imperative given the spread of the pandemic. September. It’s far too warm to hold a marathon in good faith.

The April version of the Boston Marathon (I kind of can’t believe this phrase, but here we are) has taken place for 124 years, just shy of the 148 years of weather data we have collected. It takes place on the third Monday in April, so the 15th to the 21st, during which time the average high temperature ranges from 55.9 to 59.6 degrees, and the average low (a decent proxy for humidity) ranges from 39.6 to 42.0 degrees. This is just about ideal temperature for a marathon race, and while there are obviously exceptions: ranging from cold and rainy to warm and hot, the average race weather is relatively amenable to a marathon. On average, the high temperature tops 80 degrees, which is really into the danger zone for a marathon, on average, once every 33 years.

September is warmer. A lot warmer. This is especially the case because, since Boston is near a large body of water, temperatures don’t cool off as quickly in the fall as they would inland. High temperatures in September start around 77.4 and fall to 67.0, so even the end of September is ten degrees warmer than the Boston Marathon in April. Minimum temperatures fall about the same amount, from 61.4 to 51.1. The chance of an 80 degree day is one in three at the start of the month and one in ten by the end, but again, much higher than April (for September 14, it’s about one in four, similar to early June).

Here are the temperatures for the past 10 years for September 14:

72 75 84 90 72 66 68 81 86 75

The 90 degree day would likely require race cancelation (like has happened in recent years in Chicago, Vermont and elsewhere). The Boston Marathon medical team is the best in the business, but holding the race when the weather is likely to be in the 70s will strain their resources. Holding the marathon in September is irresponsible and puts runners at an unnecessary risk. Note that in the chart below, mid-April temperatures don’t occur again until late October and early November. September is pretty much the same as June.

If we consider the other World Marathon Major races, a September Boston would be significantly warmer than any other race:

• Tokyo: Average high of 53˚
• Boston: Average high of 57˚
• London: Average high of 61˚
• Berlin: Average high of 63˚
• Chicago: Average high of 64˚
• New York: Average high of 58˚
• Boston (September 14): Average high of 73˚

There’s a good reason why the number of marathon finishers in the US peaks in October and November, with a secondary peak in April: that’s when the weather is best for running in the United States. September has a good deal of races, but most are small: the average size of a race is just over 200 participants. Moving Boston to September would more than double the number of marathon finishers in September nationwide.

The Boston Marathon used to start at noon, but was moved up to a 10 a.m. start several years ago to better accommodate the April heat. Can the race start any earlier in the day to take advantage of lower temperatures? Very unlikely: the logistics of moving 30,000 people to a remote start that early are next to impossible. The Chicago Marathon starts earlier in the day, but it starts (and ends) downtown, so as long as people can get on trains and buses to get to the start, an 8 a.m. start (with an earlier start for elite and para athletes) is possible.

Not so for Boston. Given the logistics of transportation (aha, I knew I would tie this post in with the blog), 10 a.m. is about the earliest possible start. The transit system’s earliest arrivals in Downtown Boston, where buses leave from is in the range of 6 a.m. Early-wave runners are told to be on buses before 7. Moving the start up an hour would move the start before the start of transit service. While trains and buses could be run earlier, the cost and complexity of doing so would be quite high, and without it, the downtown area would be overrun with parking and drop offs for 30,000 runners, plus spectators and other fans, on a day when many of the major streets are closed for the race.

So the race can’t be held in September without the high likelihood of high temperatures impacting the race. Late September would be better than early, although the last two weekends of the race are Rosh Hashanah and Yom Kippur, which have two major issues. The first is that it would be akin to telling many runners to run a race on Christmas or Easter (although the race does infrequently take place on Passover in April, and the day after Easter). The second is that the race passes through Newton and Brookline, and the course is home to no fewer than three major synagogues (with several others just off the course) and those two towns would likely veto either of those dates for the race. (The only option might be Monday September 21, but again, the average high that day is still 70.9 degrees, and one in six September 21s have exceeded 80 degrees.)

So that pushes the race into October or even November. This is prime marathon season: over the course of four weeks there are two other major marathons (Chicago, on the 11th, and New York, on November 1; the two largest marathons in the country) as well as the 4th (the Marine Corps, on the 25th) and the 10th (Twin Cities, on the 4th). Boston would probably want to avoid conflicting with either New York or Chicago, and might want to avoid the others. Also, October 4th is still significantly warmer than April, with high temperatures around 63 degrees. The 11th also conflicts with the BAA Half Marathon.

This leaves, in my mind, three reasonable dates for the Boston Marathon, assuming a Monday holiday is declared by the state: October 19, October 26 and November 9. Let’s look at the pros and cons of each:

October 19 makes the most sense with one exception: it is the same weekend as the Head of the Charles Regatta (which is basically the Boston Marathon of rowing). This would create a run on lodging in the region, and a run on resources. The weather: a high of 61.6, is reasonable. There are no other major races that week (although there are marathons in Maine, Vermont and Connecticut, but they are more local races) and it might be interesting to have a spotlight on Boston as the hub of the athletic universe for a weekend. But the logistics would be tricky with two major events (although it’s possible that some logistics could piggyback). Another option would be to see if HOCR would move the Regatta back a week.

October 26 makes sense except for the Marine Corps marathon. While a large race, it’s not a “World Marathon Major” race, so it probably doesn’t have the same level of conflict. The weather is a perfect approximation of mid-April, with an average high of 57 degrees. As long as Marine Corps didn’t mind Boston stepping on its toes, it might make the most sense.

November 9 is relatively late for the race, and can be cold and potentially even snowy or icy (although the average high of 53.8 is only slightly lower than April 15), but would have no major conflicts with other national races or local sporting events (the largest marathon in the northeast is the Manchester City Marathon in New Hampshire, with under 1000 runners). It would be late, but would be after foliage season, and at a time when lodging and other event space is most easily available in Boston.

Two other notes: first, the fall Boston Marathon might be significantly smaller than the spring version. The BAA will likely allow deferral to next year’s race, and many runners may take advantage, so the race might be a smaller affair, although the BAA could open late registration to more qualified runners to fill the field. After the 2013 bombing, about 5000 people were unable to finish the race and allowed deferred entry, but most of the field had already finished. This is a much larger population. It will also result in significant registration changes for next year’s race, with registration taking place after Boston, and including runners from more fall marathons, although this might be balanced by the number of races canceled this spring. The results of this will probably cascade for a few years.

Second, the BAA could potentially save resources by moving the BAA Half Marathon to the same weekend, or even day, as the full marathon. This would mean moving it from its course in Franklin Park to the second half of the Boston Marathon course, starting in Wellesley and finishing in Downtown Boston. With an early start, the half marathon racers could be mostly clear of the course by the time the full marathon finished, although it would not allow participants to run both races. Transportation would be quite simple, as the full field for the BAA half could be moved from Downtown Boston to Wellesley on half a dozen commuter trains, since the start line for the half marathon would be adjacent to the Wellesley Square train station. This, however, might put additional strain on the marathon resources, and holding the races a couple of weeks apart might be the best use of resources.