July to mid-September is prime time for heavy rains in the Southwest, where fast-rising water in narrow canyons can turn trickling streams into deadly torrents.
Check the weather Get the forecast for the entire watershed: Storms can trigger floods miles downstream. Recent rains? Be extra alert–saturated soil makes flooding more likely.
Scout for signs Water stains on canyon walls and debris lines indicate likely flood sites. Take care in areas with rocky ground that won't absorb excess runoff.
Watch the river If water suddenly gets deeper, faster, muddier, or begins carrying twigs, needles, or leaves, get to high ground ASAP. Likewise, head up immediately if you hear the roar of an approaching flood.