On the loading screen shown whilst the map is being generated, underneath the level setup, "HEADS-UP!" can appear, meaning a mutator will be activated.
ROUGH WEATHER!
There is an heavy fog preventing you from seeing too far.
RISE 'N SHINE!
It's dawn. The sun is just above the horizon and shining a colourful orange tint.
I CAN'T SEE A THING!
It's night time! Your bike has its little front lamp switched on.
WHERE'S THE PATH?
The trail has gone missing, and so are the stunts. Thankfully, a compass showing you were is the finish line is visible at the top of the screen.