When a thunder storm is forecast I always disconnect and earth the antenna. Yesterday the UK Met Office issued storm warnings for central and southern UK. A good way of tracking storms is to use an EU weather radar that gives a real time 3 hour forecast. You can pin your location making it easy to see if you are in the path of approaching weather. The storms missed this QTH, the northern edge being about 80 miles south of here.
The site is also a useful resource for predicting short term weather for portable operation. Like any weather forecasting it is not infallible!