One of the most useful tools I discovered on my trip was an iPhone/iPad application called MyRadar.
MyRadar has a free version (with a small advertising strip along the bottom of the screen) and a paid version.
I found the free version to be quite good enough. As long as you have an AT&T signal, simply open MyRadar and it will show the location of any rain showers (or snow showers) in the area. You can then ride on or hide out, whichever you like.
The image below is tropical storm Hermine last September. I ‘rode on’ for an hour and then hid out for the next 24. My location was the ‘dot’ between San Antonio and Kerrville.