Rail services provided by First Capital Connect are still being affected following major damage to overhead power lines between Elstree and Borehamwood yesterday.
The company says the damage has meant fewer trains are able to run on some lines.
Train services running through these stations may be cancelled or delayed by up to 30 minutes at short notice and disruption is expected to continue until 6am tomorrow.
The damage to lines near Radlett is impacting trains across the whole Thameslink route today.
Trains are only running on 2 out of the 4 lines between Radlett and St Albans in either direction and FCC expects that will remain the case for the rest of today.
Other rail companies are carrying customers via any reasonable route until further notice.