If your dates are Presidents' week, shift right rather than left
The asymmetry in this week is the useful part. Attendance ramps into Presidents' week over several days as districts release at slightly different times, but it clears in about two days afterward, because a synchronized break ends synchronously. That means the week after is materially quieter than the week before at the same ticket tier.
If the dates are genuinely fixed to the holiday week, the highest-leverage decision is which parks you take on which days. Magic Kingdom and Hollywood Studios absorb a holiday crowd worst; EPCOT and Animal Kingdom absorb it best, because EPCOT's festival footprint spreads people around World Showcase and Animal Kingdom's acreage swallows them. Put the two hardest parks on your arrival Sunday and departure Friday, not on the Tuesday and Wednesday in the middle.
At Disneyland the equivalent move is to buy the park hopper and use it in reverse — Disney California Adventure in the morning while everyone queues for Disneyland Park, then cross over after dinner.
Four festivals, and a changeover worth targeting
February is the only month that can put two EPCOT festivals in a single trip. The Festival of the Arts runs into late February and the Flower and Garden Festival opens at the end of February or the start of March, and in some years the two overlap by a handful of days. Treat that overlap as a bonus if it happens rather than as something to book around, because the changeover dates are not published far enough ahead to plan against.
The Disney California Adventure Food and Wine Festival also opens in the back half of the month, which means the last week of February can hand you festival marketplaces at both resorts. Nothing else on the calendar does that.
The practical note on all festival marketplaces: the booths open with the park or shortly after, and they are close to empty for the first two hours. Anybody who eats their way around World Showcase before 1 PM has a completely different experience from somebody who starts at 5 PM.
Lunar New Year at Disney California Adventure is a walk-up event
The Lunar New Year celebration runs from mid-January into mid-February and uses the same marketplace structure as the resort's other festivals, plus a procession that runs a few times a day rather than continuously. No ticket is required beyond park admission.
The actionable detail is showtimes. The procession's weekday early-afternoon runs have room along the parade route; the evening and weekend runs do not, and people stake out curb space forty minutes ahead for them. If seeing it matters, take a weekday and take the earlier showing.
The food here is better value than the equivalent booths at EPCOT and the lines are shorter, which is a reasonable argument for putting a Disney California Adventure day in the front half of a February Disneyland trip.
Rain is Disneyland's best crowd control, and it is survivable
Southern California rain empties the park in a way Florida rain does not, because Anaheim's crowd is heavily local and locals with passes simply come back another day. Disneyland keeps most of its capacity running in rain — the indoor dark rides, which are the bulk of the roster, are unaffected — so a wet Tuesday in February can deliver waits you would otherwise need to visit in September to see.
Pack a poncho, not an umbrella. Umbrellas are unmanageable in a switchback queue and several attractions will ask you to collapse them anyway. Waterproof shoes matter more than a waterproof jacket, because standing water in the walkways is the part that ends the day.
The attractions that do close are the outdoor ones with exposed track and the aerial ride at Disney California Adventure. Build the wet hours around New Orleans Square and Fantasyland and save the outdoor headliners for the clearing.
Book dining before you book anything else this month
February compresses two dining problems into four weeks. Valentine's weekend removes most of the table-service availability at both resorts, and Presidents' week removes the rest. The reservation window opens well ahead of either, and the good tables are gone within minutes of it opening for those specific dates.
The non-obvious workaround is lunch. Signature restaurants that are impossible at 7 PM on Valentine's weekend are frequently available at 11:30 AM at a lower price for a nearly identical menu, and a midday table also solves the problem of what to do during the busiest hours of a busy day.
If the reservation does not materialize, the festival booths are a legitimate dinner. That is more true in February than in any other month, because there are marketplaces running at both resorts simultaneously.