Sarabi's Tears

With the Outlander exiled and Kiara brokenhearted, Simba felt lost. He left Pride Rock and sought solace amongst the savannah plains. Soft rain pelted his golden fur, and he looked up to see the clouds swirling together, creating a familiar form.
"...Mom?"

The Great Queen of the Past visits her son, mourning the events that have taken place. If you watch SP, Simba is not seen from the Exile seen to right before the battle, when he walks into the den as Timon and Pumbaa are arguing. So... perhaps he went for a walk. ;] And this would explain the "oh-so-chiché" rain during the battle.