Cutting wet grass is not ideal. It’s more prone to clogging the mower, can cause the blades to dull faster, and can spread diseases and pests.
Risks include limiting air circulation which increases humidity, creating water-logging in soil, and aggravating disease pressure. And it leaves clippings too thick to break down quickly.
The best time to mow is after a light shower, when the grass has had time to dry out. In dry conditions, set your mower at a higher setting instead of scalping the turf and water it after you finish cutting as an added benefit for healthy grass growth.
To reduce potential problems from cutting wet grass, use sharp blades and keep your mower height high. Make sure it’s properly serviced before cutting. Take care not to leave clippings on sidewalks and driveways which will become slippery when wet; instead use a sweeper or blower if needed.
In colder climates where winter holds moisture longer into spring than in warmer regions you may find yourself with no other choice but to cut wet grass if you wish to maintain a healthy green lawn. Do so carefully assess all risks damp weather brings with it before cutting.