Heavy rains are poised to cause the worst flooding along the Russian River in Guerneville in Northern California in more than 20 years.

Here is what you need to know:

Q: What is the outlook?

►About 4,000 people living in about two dozen areas near the river were ordered to evacuate Tuesday as the river started to flood. It’s expected to crest at 46.1 feet — more than 14 feet above flood stage — Wednesday night.

►Some areas north of the river got nearly 10 inches of rain as of Tuesday. The National Weather Service said the new storm produced more than a foot of rain in the hills above Healdsburg.


►Localized flooding was reported Tuesday night along some creeks and rivers in Sonoma County. But the situation is expected to get worse Wednesday.

#RussianRiver at #Guerneville forecast to peak at 46.1 feet late Wednesday evening (major flood). This would be the sixth highest level on the Russian River in Guerneville, and the highest since 1995. #CAwx #CAflood #CAstorm pic.twitter.com/9zFQyyBXjT — NWS Bay Area (@NWSBayArea) February 27, 2019

Q: What are the dangers?

►Authorities warned residents to be vigilant to cracks in the roads, leaning trees and the sound of trees cracking. Roads may become impassable, and people who don’t leave immediately could be trapped, they said.

►Officials staffed extra deputies and dispatchers to help with evacuations and field emergency calls. Two boats were deployed to the lower Russian River to help people get out.


Q: What does history show?

►The Russian River has seen numerous serious floods during wet years.

►One of the worst in Guerneville was in 1995. That year, the river crested at about 48 feet, 16 feet above flood stage. The Times reported then that there were mass rescues: “Many of those forced to flee Guerneville said they were caught off guard by the river’s rapid rise…. Some left by small craft, floating past debris as they sought higher ground. Others boarded 2½-ton National Guard transport trucks that drove through the floodwaters. One even hitched a ride on a trash bin floating by.”

Russian River at #Guerneville could crest nearly 14 ft above flood stage...Note at 45.9’ that’s near the level where downtown would flood. Expected to go flood stage later today, crest would be Wed night/Thu AM. Hydrograph forecasts are being continuously updated, Stay tuned... pic.twitter.com/kLeoOn7VNx — Rob Mayeda (@RobMayeda) February 26, 2019

Q: How about burn areas?

►Sonoma County was hit by devastating wildfires in 2017 that burned thousands of homes and charred many hillsides and canyons.


►Officials say they are also concerned about mudslides, especially in the hillside neighborhoods along the river and areas ravaged by recent wildfires. One debris flow sloshed across a roadway in the Monte Rio area on Tuesday evening, but no one was injured.