The annual spring ride refurbishment is underway at Disneyland, something that happens every spring as Disneyland does maintenance ahead of the busier summer season. This generally effects the bigger attractions, also if minor changes need to ne made they do it at this time of the year.
One classic ride closing later this month for refurbishment is the Matterhorn Bobsleds which are due to be closed for a short while for February 28th to March 4th. Other rides due to close this spring are the popular rides Pirates of the Caribbean as well as Splash Mountain.
If you are a fan of the Indiana Jones Adventure, it is closing for a short time in March from March 8th to March 11th. These down times are usually accurate but occasionally they do go over so I would check that your must-see ride is open so not to be disappointed.
Generally spring is a slower time of the year at Disneyland and California Adventure but with the huge crowds at the California Disney Resorts this year there isn’t really a slow time.