Predictions are shown in Mountain Time.
Eruptions cannot be predicted with absolute certainty and estimates are derived from user reports.
GeyserPrediction
CastleNPS 03:00 ± 1 hour
CastleGeyserTimes 03:19 ± 1 hour
GrandGeyserTimes 02:49 ± 1 hour

Predictions courtesy of:

GeyserTimes GeyserTimes
NPS National Park Service

(*) Prediction derived from double interval