Wigan commuters are set for more travel disruption this week after "extreme Autumn conditions" resulted in services being cancelled, delayed or short-formed.
In a statement on social media, rail bosses said: "Due to the excess leaves on the line, some services will be busier than normal this week. Customers are advised to check before they travel and we are sorry for any inconvenience.
"We're sorry several of our trains have been shorter and more crowded this week. Autumn conditions means the rails are slippery which can lead to flat spots on train wheels.
"Our depot teams are working round the clock to repair them and get trains safely back into service. Network Rail also operates special trains throughout Autumn to improve conditions."
Northern's issues had added to "a national crisis," according to RMT General Secretary Mick Cash.
He said: "With Waterloo closed and London and the South plunged into rail chaos this morning RMT is now picking up reports of wholesale cancellations on Northern Rail due to a shortage of fleet, reinforcing the point that this is a national crisis.
"Both Arriva Rail North and South Western Railway have a track record of hacking back on staffing and budgets to bump up profits and today's Monday Meltdown is the consequence of their actions. Neither of them are fit to run a bath let alone a railway. The case for public ownership is now overwhelming. "
Wiganers are advised to check the Northern website before they travel for full details about changes to their services.