Honolulu is taking no chances on possible flash flooding, which is bad news for residents near streams but good news for anyone who gets out ahead of it.

• The city opened four emergency shelters on Oahu, including one near Manoa District Park, for residents who feel unsafe staying home.
• Crews cleared streams and opened stream mouths ahead of expected heavy runoff, and extra high-water rescue vehicles are on standby.
• Ground is still soaked from months of past rain, so new rain can run off and flood faster than usual, even though a nearby dam is unusually low right now.
• One stream spiked overnight, nearly doubling in height before dropping back down, showing how fast conditions can change.
• Officials are telling people to report flooding through the city's 311 app and to pack medications, food, water, and pet supplies if they head to a shelter.

Outlook: Officials expect streams to stay unpredictable and are urging residents to have an evacuation plan ready rather than wait for conditions to worsen.