KD Rhine cruise - mid April or early October?

Both are good options. For the Rhine cruise, both options are probably available on a shoulder season schedule; for scheduling yourselves you will want to pay close attention to the 2025 K-D and the Bingen-Rüdesheimer schedules once they come available.

I worked some years in Bonn and find it harder to give advice for a good spring travel time than for a good autumn travel time because the last window is larger. The cherry blossom in Bonn varies from year to year; this year it was very early around April 5 (see report in German). in 2023 it was around 10 days later (example).

A main advantage of traveling the region in September / October are the numerous local wine festivals but I do not know if you have the chance to visit them while on a cruise.

I would go in the fall, the foliage and colors will be much more developed than in April. We did one trip in May and decided not to do another one for that reason. As for the weather and river level aspects, it's all pretty much a crap shoot these days with the climate change going on.

The weather has turned cold, and the trees are already changing color and losing their leaves in the areas you're interested in. That being said, last year we had snow in late April. Due to the early cold snap people are predicting a long, cold, winter, which we have not had for several years.

I think, based on the Paris/Alsace/Germany route, you would be better off looking at a Moselle cruise vs. the Rhine. I think it's prettier, the wine is better, there are more castles, and it's the one I see more European tourists on. You can easily get on a boat around Trier and go downriver (northeast) from there.

Thanks everyone! I appreciate your insights. I think I will save this trip for next October. I think we will stay in Rüdesheim for a few days, and take the KD Rhine cruise from Rüdesheim to St. Goar, and then train back to our hotel. I will try and catch a wine festival too!

You plan to "take the KD Rhine cruise from Rüdesheim to St. Goar, and then train back to our hotel."

The trains from St. Goar will not get you there... St. Goar is on the opposite riverbank, so you will need to either...

1) Get off the cruise boat in St Goarshausen and catch the train back from there, or...

2) Get off the boat in St Goar, then at some later time cross the river to St. Goarshausen using the Loreley Ferry, which shuttles back and forth across the river all day long. Cost is a couple Euros. Then catch your train back to R'heim.

Or you can take the train from St Goar to Bingen, and even stop at the towns on that side of the Rhine, and then walk from the train station in Bingen to the ferry and go across back to Rüdesheim.

"...walk from the train station in Bingen to the ferry and go across back to Rüdesheim."

This is possible, but not without its complications...

• The normal passenger ferry, while it may sometime go back into service, has not been running for a very long time. I would not count on it. The B-R cruise boats - operated by the same company that runs the ferry - can currently be used to make the crossing from the B-R cruise-boat dock (known as "Brücke 4".) This dock is an easy and quick walk from the Bingen Rhein Stadt station (Bingen has 3 train stations.) The schedule for these boats - see table, bottom right under "Personenfähre" - is not particularly regular or comprehensive, however,

• The car ferry (Autofähre,) which I assume KGC is suggesting, is running and accessible for foot passengers, but the location is at the extreme downstream-end of town. You can see the locations of the two ferry crossings (marked with little blue anchors) on this map so you would certainly want to be careful to get off the train at the Bingen Rhein Stadt station for this walk.

St Goar / St. Goarshausen, by comparison, is a snap...

• ST GOAR: One ferry dock for both cars and foot passengers (#2 on the St Goar map below) straddled by the K-D cruise dock (#4) on one side and the B-R cruise dock (#1) on the other. One train station, only a few steps away from the docks:

https://www.rheingucken.de/goar/stadtplan-st-goar.html

• ST GOARSHAUSEN: similarly small, slightly longer walk from docks to train station than in St Goar. see map:

https://image.jimcdn.com/app/cms/image/transf/dimension=820x10000:format=jpg/path/sd67acee2a63c85f6/image/i59f4e1787010b221/version/1527493774/image.jpg

KGC refers to St. Goar and suggests visiting "the towns on that side of the Rhine..." The nearest towns of interest on the St Goar are...

Boppard (10-12 train minutes to the north of St Goar)
Oberwesel (5 train minutes to the south)
Bacharach (10 train minutes to the south)

Each of these places is worthwhile, IMO. Have a look to see what interests you.

I'd like to point out one final option for getting back to Rüdesheim from the St Goar side - the K-D cruise boats. The boat ride back to Rüdesheim is long from St Goar- like 3 hours. But let's say you took a morning cruise with K-D to St Goar, and you then used the train to visit Oberwesel and/or Bacharach. You could board the southbound cruise boat (which left St Goar at 16:10) at either 16:40 in Oberwesel... or in Bacharach at 17:20 - and reach Rüdesheim at 19:00. The additional cost for a round-trip cruise ticket is only €3 each. Besides being cheap, it's a whole lot simpler than traveling via Bingen and using the train + the auto ferry strategy.

https://www.k-d.com/

Cruising on the Mosel: a nice idea if you have the time. The scenery is nice - it's more about smooth sailing and bucolic scenery than about dramatic cliffsides and swift current, which better describes the Rhine. However, unlike the Rhine, Mosel cruising tends to be interrupted regularly with stops to pass through the LOCKS that must be negotiated. There are 12 of them between Koblenz and Trier. It's not remotely possible to cruise this river in a single day, and cruising even a segment of the river will turn up at least a lock or two. So you might want to choose your cruise segment carefully.

The other thing about the Mosel - and this is true of the Rhine as well - is that only certain segments are popular enough with the public for a generous cruise schedule. Parts of the Mosel have no boats at all. And October cruising is skimpier than ever. From TRIER, as was previously suggested... The main provider of Mosel cruises (Kolb) offers no October cruises at all going downstream to Bernkastel. Going upstream to Saarburg is possible, but there are only two cruises per week, one on Wednesday and one on Sunday, and the 2-hour one-way cruise hits two locks on the way.

Kolb's Trier Schedule: https://www.moselrundfahrten.de/cams/clients/kolb/media/downloads/file_31.pdf?1716814390

This cruise company takes folks into Luxembourg, but not in September:
https://www.entente-moselle.lu/en/bateau-princesse-marie-astrid/presentation

IME the best Mosel cruising happens between Bernkastel and Traben-Trarbach, where an ample cruise schedule serves the public in October and into early November as well. See this schedule below:

https://www.moselrundfahrten.de/cams/clients/kolb/media/downloads/file_1.pdf?1713965549

Instead of Rüdesheim I recommend Eltville for a few days' stay.