Outdoor party lights keep burning fuses
I would say it is not safe to replace the fuse with a higher amp fuse. If the fuse is 15 amps, that means the wiring can handle 15 amps. If you allow too much current over too little wire, things get hot, fast. You definitely don't want an electrical fire. So let's troubleshoot the problem instead...

If you're running a lot of those strings and there's other stuff on the circuit (e.g. a fridge or air conditioner) you might be overdrawing and tripping the fuse. 


What else goes out when the lights go out?
How many strings of lights are you linking?
How many amps is the fuse that keeps blowing?