In the mean time, back in late September I paid a visit to Nancy and Norcross Ponds in the White Mountains of New Hampshire.
This is a fairly simple day-trip (maybe 1500 feet of up), which (for better or worse) gave me an opportunity to assess the quality of my rain gear. On the way up, I caught occasional sprinkles, but it started to rain properly near Norcross Pond (the destination point -- I am pictured below its outlet in this photo). After about 20 minutes, the rain stopped, and I was blessed with about 30 minutes of "partly sunny" in which to explore the pond and take some pictures.
However the rains restarted, and for the next 90 minutes got progressively worse, culminating in a 10-15 minute downpour. Fortunately the rain stopped by the time I got back to the car. But my "rain gear" (which wasn't really high-quality rain defense) was soaked completely through. We'll be taking better gear to Peru and Chile.