The weather is sometimes a factor when a construction project is ongoing. The issue with this is that the contractor can't control it, but they still need to make contingency plans will enable them to have the project done on time despite what is going on with the weather. This might not be easy, but an experienced contractor should be able to make it work.
There are many ways that a contractor can plan for bad weather. They might work a few rainy days into the work schedule. Another option is to plan for projects that can be done when the weather isn't optimal for other work. When aspects of the project are indoors, those can be the focus on bad weather days.
You shouldn't have to adjust your schedule because of this factor or other delays. There is a chance that a delay in the project might require you to move a grand opening or another event back. This costs you money if you're running a business. If the project is a personal one, there is a chance that the delay could cause you stress.
We know that you just want your project completed on time and as intended. One thing for you to watch for is the contractor or subcontractors rushing through parts of the project in a way that might lead to them doing a subpar job. While this won't happen with a reputable contractor, it is possible with ones who are trying to make a quick dollar. Taking legal action might be necessary if there are extended delays or low quality work.