Could be lots of things;
- maybe corrosion from wet weather is interfering with the connections, you might try spraying exposed wire connections with contact cleaner (but be careful as this can remove some finishes, so wipe up)
- your charging may have blown a fuse, look for fuse boxes and connections in lines from your battery. You may have to replace more than one so check them all. You might be able to tell if nothing comes on (like your headlight or other lights)
- could be something more serious that's electrical, but you would need a shops help for that, not mine,