But other resiliency changes on which the M.T.A. spent big are not fixing the city’s current threat of heavy rain; the Sandy-era fabric gate for the A-train tunnel has never been used outside of drills, and that kind of technology isn’t very effective at closing subway openings off from quick, shifting cloudbursts. M.T.A. leaders talk often about “multihazards,” how a host of climate horrors will shape the subway. This summer, some of the city’s flash floods occurred after extreme heat or days of wildfire smoke from Canada that hovered uneasily over New York. Those forces test the subway, too. Covering sidewalk vents with heavy mats may keep water out, but should be “temporary,” Wilson says, while people like him work toward more complicated architectural solutions. Covered vents mean less circulation — and more heat.

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