The RMT union has announced that further industrial action will take place on Thursday 18 and Saturday 20 August. The effect of this will be very similar to the strike action that took place in June and July. Govia Thameslink Railway (GTR) are advising customers to only travel by rail if their journey is absolutely essential.
Services at Billingshurst, Christ's Hospital, Faygate, Horsham, Littlehaven and Warnham stations will not be operating on Thursday or Saturday. Services at Balcombe will be reduced to two trains per hour in either direction on both days.
I am afraid services on Friday 19 and Sunday 21 August will also be disrupted as RMT members will not work overnight shifts that begin on strike days. The first trains on all routes will be after 07:15, in some cases significantly later, and a reduced frequency service will run throughout both days.
Separately, RMT members at Transport for London and London Overground are expected to take strike action on Friday 19 August. This will severely affect travel in the inner-London area, but is not currently expected to have a significant impact on GTR services other than through busier services.
Up to date travel information is available here: https://www.nationalrail.co.uk/.
Further information on the industrial action, including ticket exchanges and refunds, can be found here: https://www.thameslinkrailway.com/travel-information/plan-your-journey/industrial-action.
Please see the below file for GTR's diagram of services running on 18 and 20 August.