If it raining in your area, the rain itself will not impact your viewing experience, but it is what typically comes with the rain that can be problematic. You need the sun to be out to see the solar eclipse so rain clouds can damper your viewing experience.
Eclipse2017.org explains how weather impacts your solar eclipse viewing experience:
Yes, it’s important that the weather co-operates — if you can’t see the sun, then you won’t see the eclipse! It’s important to watch the weather forecasts intently in the days before the eclipse. Eclipse chasers who travel around the world are sometimes stuck in the location they’ve chosen, and so they plan meticulously to seek out the most likely places where the weather will be clear. We have much more flexibility in travel here in the USA, but you should still keep watch.
While the rain makes it uncomfortable for viewers to stand outside to watch the eclipse, what you need to be worried about is the clouds.
As far as other weather elements, you could experience a temperature drop during the eclipse. NASA details how to measure the temperature drop in your area. In past total solar eclipses, history suggests the weather can drop drastically during the eclipse.
Space.com details the drop in temperature that has been experienced in past solar eclipses:
During the total solar eclipse on Dec. 9, 1834, the Gettysburg Republican Banner reported that in some places, the eclipse caused the temperature to drop by as much as 28 degrees Fahrenheit, from 78 degrees F to 50 degrees F (25 degrees Celsius to 10 degrees C). During a total solar eclipse on the Norwegian island of Svalbard in March 2015, temperatures dropped from 8 degrees F to minus 7 degrees F (minus 13 C to minus 21 degrees C).
The change in temperature during a total eclipse will vary based on location and time of year. The temperature change created by the loss of light from the sun’s disk will be similar to the difference between the temperature at midday and the temperature just after sunset, except the change will occur more suddenly, which is why this is often one of the very noticeable effects of a total solar eclipse.
South Carolina is one of several states on weather alert as several parts of the states call for clouds and rain. As thousands of people have traveled to different states to put themselves in the best viewing location, here’s hoping the weather cooperates.