The author vaguely remembers the desert hikes he has taken in perfect weather. However, he has crystal clear memories of the day he spent dodging lightning on Little Blue Table, the day of 40 mph winds on the Wapi Flow, the day he barely escaped Laidlaw Park ahead of a horrendous thunderstorm, the day when, with water bottles almost empty after a warm but windy day, Hells Half Acre became unbearably hot as the sun went down and the breezes died...

These weather events should have been forecast by newspapers, radio, and television--and perhaps they were. However, the author sometimes takes a chance that the forecasters are wrong. Why? Because Idaho meteorologists are notoriously inaccurate. Their main excuse is that weather fronts frequently stall or speed up as they cross mountain ranges on their approach to Idaho. A front that looks 30 hours away may arrive in 12 or 60 hours. Another problem is that predictions are geared to urban or agricultural areas, not the backcountry.

Above all, dumb luck will often determine whether you win or lose the percentages game. A narrow band of thunderstorms may hit or miss the dirt road that leads to the place you want to hike. You must be flexible, and always have a backup hike or two in mind.

To plan your Spring or Summer or Fall hiking campaigns, carefully study the climate charts, which I have taken from the outstanding site www.wrcc.sage.dri.edu/climsum.html. Visit yourself to get the most up-to-date information, or for information on sites closer to you.

Each site has three climate charts. The first is a smoothed summary of daily high, low, and average temperatures; it covers the period 1961 through 1990. The second is an unsmoothed chart of daily average temperatures, plus record daily highs and lows. It covers the entire record "period of observation" for the site, ending with June 30, 1997. The third is an unsmoothed chart of daily average and record precipitation, for the period of record. Together, the second and third charts help you prepare for the worst possible weather. (And, the third chart can reveal amazing things, such as the fact that it never rains at Craters of the Moon on April 10.)

The climate charts are based on seven sites, which are shown on the index map above. They were chosen for their elevation and location: Lewiston and Weiser cover Hells Canyon's ends; Bruneau and Mountain City cover Owyhee County from low to high elevation; Bruneau and American Falls cover the Snake River Canyon; American Falls and Craters of the Moon lie at the north and south ends of the lava fields, and Craters and Dubois cover the upper Snake River Plain.

For the weather for the specific days you want to hike, listen to weather radio, watch your local TV, watch the Weather Channel, or go on-line to the National Weather Service at www.boi.noaa.gov. At any rate, be sure to check the weather when you head for the desert--and be sure to trust your own powers of observation.