Predictions are shown in Mountain Time.
Eruptions cannot be predicted with absolute certainty and estimates are derived from user reports.
GeyserPrediction
GrandGeyserTimes 15:53 ± 105 minutes
CastleGeyserTimes Jan 21 @ 01:07 ± 1 hour
CastleNPS 13:00 ± 45 minutes
GrandNPS 15:45 ± 90 minutes
Old FaithfulGeyserTimes 12:13 ± 13 minutes
Old FaithfulNPS 12:18 ± 10 minutes

Predictions courtesy of:

GeyserTimes GeyserTimes
NPS National Park Service

(*) Prediction derived from double interval