How Weather Drives the Boston Cutoff
The cutoff is not just about how many people run marathons. It is about how many run fast, and weather is a big lever on that.
Cool years feed the cutoff
When the big fall marathons get cool, calm conditions, thousands of runners set personal bests on the same weekends. Those fast times flood the qualifier pool and push the cutoff up. A hot year at the same races suppresses fast times and can soften the cutoff.
What it means for you
You cannot predict the weather a year out, which is part of why the cutoff is hard to forecast and why the 2027 estimate carries a wide range. The defence is the same as always: build a buffer big enough to survive a fast year. See how much margin recent years demanded in the predictor.
Frequently asked questions
Does weather really affect the Boston cutoff?
Indirectly but meaningfully. Cool weather at major qualifying races produces more fast times, which raises the cutoff.
Can I predict the cutoff from weather?
Not reliably a year ahead. It is one reason cutoff predictions carry wide uncertainty. Build extra buffer to be safe.