Complain to the service provider, and they will have it rectified if the problem is at their end. It can take a few days. If the problem is just at your residence you might have to get a new router.
Remember to turn off and unplug all devices whenever there is thunder. Even if it is during the middle of the night.
Another point we have to take care is earthing connection to all electrical appliances. If earthing is not good also this will happen. If your house earthing is not done properly some time if you touch the house walls when they are wet you will feel shock. So always a proper earthing is necessary.
Inform your service provider and get it rectified.
We have to turn off all electronic items and remove plugs from socket when their is big storm. Also people have make sure that earthing has done properly otherwise we will het shock when using some electronic items or when we on the switch.
The cable TV providers always give notice to disconnect the set-top boxes during lighting and rains. It is always better to unplug and disconnect all electrical appliances during lightning and thunder. It is better to do that when the first lightning occurs or we can see that rains and lightning are coming soon.
I had my set top box and a fan damaged once. After that as far as possible I am taking precautions and unplugging them.