EDIT/WARNING: Note that you may want to take care not to complete too many regular PR challenges until you get this achievement. It seems that this may not unlock if you previously surpassed the seasonal goal on an event before the seasonal challenge went live and you could glitch yourself out of earning this achievement. Please see comments for more information.
These are pulled from the same pool as regular PR challenges (Speed Trap, Danger Sign, etc.) but with an additional requirement beyond the three star requirement attached. Only one (or even none) may be active at any given time, and what is active seem to rotate within seasons as well.
Obviously you'll need to have gotten through the first four seasons and joined the Horizon roster before these will appear, like 90% of the game's features.
The easy way to see if one is active is to go to the map, hit RB and select only Seasonal PR challenges. Then scroll around until you see a pink icon lit up. If you hover over it you'll see the 1, 2, and 3 star requirements followed by a line underneath with the seasonal requirement. In my case, for example, a danger sign that had a 550 ft requirement for 3 stars had a 750 ft requirement for the seasonal version. These requirements tend to be very difficult; I barely made it at 751 ft when I unlocked this, with a fully tricked out X 999 Bugatti Veyron!
As always, rewind to your advantage and if it's too difficult, wait until it rotates to a style that's more achievable to you.
EDIT (2018/10/12): It seems that this achievement is very finicky. If you're having problems, please read the comments for others' tips.
EDIT (2018/10/21): @Swooshiain: "The Playground Games community liaison has acknowledged that they are aware of the problems with this achievement, and they are looking into it."