As always it's very difficult to predict the weather and what may or may not happen over the next few days. What we do know is that the Central Disaster Steering Committee started releasing large quantities of water from the hydro-electric dams from the 19th November in preparation for the high rainfall expected over the coming days.
Image: Vu Trong Phan

Hoi An
Last nights spring tide was a good test for what's to come, and at peak high tide flood water levels were minimal. In the old town - only riverside Bach Dang St was affected. This morning river levels here are still low despite heavy rain and flood warning levels at time of typing are on level one.*
River levels are expected to rise a little today and the main focus remains set on the rainfall expected on the 23rd/24th November. We can expect a few more wisely timed dam releases to help cope with that over the next 48 hours and with any luck, old town floods will be minimal with very few sites, businesses and attractions affected.
Our advice for Hoi An remains the same, if possible book a hotel outside of the flood zone for peace of mind, if your visit coincides with the high rainfall expected on days 23 & 24 November - keep an eye on updates and prepare to be a little flexible with travel plans if required. Expect lots of rain..
*Flood warning levels range from one - three. When they breach level two, it's a good idea to evacuate hotels located on low ground to save yourself a boat rescue.
Hue
For Hue updates Matt @ https://www.facebook.com/nookcafebarhue will happily answer any questions on the present conditions in the city. From our office in Hoi An we can only provide information on the dams and river levels. Currently river levels are down on yesterday although they are releasing overflow from the four dams that feed Hue's rivers. Warning levels are set at two and the rainfall in the city is minimal (though there is rain in the mountains, yesterdays big release should have things under control for now).
Transportation
A few landslides have occurred between Hoi An and Hue. One in particular on the Hai Van Pass has caused some problems and heavy delays with rail travel, though it has now been cleared. During the last floods the main highway was closed to traffic. We'd recommend avoiding a land commute between the two cities if at all possible over the next few days, or allowing some extra time for delays. Flights will not be affected and the coastal road between Da Nang and Hoi An is fine.
For hotels on high ground in Hoi An: - https://www.coastvietnam.com/hoiantravelforum/hoi-an-hotels/the-importance-of-choosing-the-correct-hotel-in-flood-season
And to help get to grips with the flood basin that is Hue:-
http://www.floodmap.net/elevation/ElevationMap/?gi=1580240