How does rain affect horse racing?

Related questions

1. Are horses faster on turf or dirt?
2. How cold is too cold to ride a horse?
3. Can horse flu kill?
4. Do Secretariat records still stand?
5. Has the derby been Cancelled?
6. What time is the Preakness 2018 Main race?
7. What horse won the Preakness 2018?
8. What time is the Belmont Race 2018?
9. What is post time for the Preakness 2018?
10. What did secretariat die of?

Tags

1. #horses
2. #surface
3. #could
4. #preserve
5. #typically
6. #cases
7. #yielding
8. #track
9. #falling
10. #course
11. #scratch
12. #those