When the weather turns around and it doesn’t stop raining you can have multiple problems with your lawn no matter whether it is:
The first thing to do is get the ground hard, hire a roller to compact the ground to stop the ground from taking in moisture. It’s also a good idea to check to see if your drainage is up to scratch and there is no water sitting anywhere, water logging will cause the grass to rot.
Pick up your lawn clippings, leaving them on the grass can generated fungal issues causing your lawn to get sick
Keep an eye out for grubs, if you see sections of your lawn dying off in patches you may need to treat your lawn for grubs when it constantly rains the grubs come from the deeper soil to breathe, they also feast on the root system of your lawn.
To sum it up:
Feed your lawn
Mow and pick the clippings up
Check your Drainage
Check for fungus related growth issues
Check for Grubs