There’s a fairly simple technique the cyclist can employ to make a rough estimate of the influence that rain may have on a particular trip. The National Oceanic and Atmospheric Administration publishes a list of cities and their average number of days with precipitation for each month of the year. October in Seattle, for instance, has an average of 13 rain days, or nearly one-half of the month. If a cyclist is determined not to ride in the rain at all, he would have to allow at least three or four layover periods for every week of Seattle-area riding. October in San Francisco, on the other hand, averages five days of rain, or roughly one-sixth of the month. Here, you could reasonably hope to keep layover days down to one or two a week.
