Just in dreams. It's not consistent or predictable, but Buffy in particular has shown an ability to predict the arrival of serious troubles before they arrive.

However, the power cap has had the proportionate effects on her dreams, or so she's told me.

[Giles was about to leave the kitchen, maybe lead Helios back to the apartment. That stops him dead, however.]

...visiting Paprika is, um, generally adviseable, under these circumstances.

...I'll help however I can until we can talk him round.