Ask Mr. Smarty Plants

We can really only speak in generalities, because so many different problems can causes some of the symptoms you have described, in both trees. You did not mention noticing any insect infestation on either tree, and the rather "sudden death" of a branch or a large part of the tree indicates something more abrupt than insect problems.  

The Catalpa speciosa (northern catalpa) is native to North America, and therefore is on our "good" list, and in our Native Plants Database. It is not native to Wisconsin, but has been introduced there and, in some cases, escaped cultivation. In the Wisconsin Botanical Information System, this tree is shown growing in southern Wisconsin, which would include Jefferson Co. About the only thing it says that could cause the problem there is "twig blight," and we would call sudden death of the lower branches something more than twig blight. 

Acer saccharum (sugar maple is native to Wisconsin and apparently also grows in southern Wisconsin. This USDA Forest Service website, Acer saccharum will give you more general information about pests and diseases. The common pests of the Sugar Maple are leaftstalk borer and  petiole borer. The leaf stalk shrivels, turns black and leaf blade falls off. The maple can also suffer from anthracnose or verticillium wilt, which causes the wilting and death of branches. In another source, we learned that a heavy load of snow on a branch can cause splitting and breakage.

With both trees, since they both have lost or are losing branches abruptly, we need to consider the environment in which the roots grow. Most trees do not do well planted too close to concrete, like driveways or streets. The heavy rains you have been having could also be causing root problems if the drainage is not good. Root rot disease that destroys feeder roots, diseases that clog the vascular xylem tissue (water conducting tissue), and damage to the trunk of the tree by insects, disease, and/or mechanical means can result in sudden wilting and death of twigs and branches. These factors are usually very serious and frequently result in death of all or part of the plant. Brittle, inflexible, and shriveling twigs and stems are a sure sign of severe damage. Sudden drought, herbicides, or other environmental conditions can also cause leaves to wilt and drop. If the damage is slight and twigs remain green and flexible, the plant may recover; if severe, death of the plant will result. Another problem can be root girdling. A plant that has been in a pot too long before it is transplanted will sometimes have roots growing in a circle. As these roots mature, they will eventually begin to choke the tree and, again, die-off will occur. 

Obviously, at this distance, we can't hope to diagnose a specific problem because there are too many different things that could be causing the same result. We would recommend that you call in a trained arborist who can better tell you the prospects for recovery of your trees, whether they can be treated or if they will have to be removed. Or, contact the University of Wisconsin Extension Office - Jefferson Co., Wisconsinline Gardening. If the wet weather has been causing similar problems in the area or some specific insect or disease has been attacking other trees, they will at least be able to steer you in the right direction.