Want to go to Cinque Terre from florence for the day

Personally I don't think it is workable and especially if you are thinking about hiking between a couple of cities. And CT is an area and not a city. The train between Florence and LaSpazia is about 2.5 hours so that takes six hours of your day. At best you could do would be a trip to one of the cities in CT, walk around a bit, have lunch, and return. I would not attempt it.

To get there early in the morning you need to take the FrecciaBianca high speed train that departs from the Firenze Campo di Marte station at around 07:30. A car cannot be as fast.
Then you can come back with any train after dark.
Be aware that in case of inclement weather the Park trails close down.

Check schedules on
www.trenitalia.com
Enter from FIRENZE (Tutte le stazioni) to see the departures from all stations including Campo di Marte.

What hike are you hoping to complete? Parts of the coastal path are still closed ( Riomaggiore to Manarola to Cornelia). So what is left is Corniglia to Vernazza to Manarola.

If you depart Firenze at 7:28 am you would arrive in Corniglia 3 hours later, around 10:30 am.

That weekend is a particularly poor choice if the weather is decent. In 2018, Easter weekend set a visitor record for Cinque Terre with over 100,000 visitors to the 5 tiny villages. The wonderful city of Lucca would be an easier but memorable excursion. Back to your post: this very question was asked recently and discussed here: https://community.ricksteves.com/travel-forum/italy/cinque-terre-day-trip-from-florence-4ef06341-e6fa-4e3b-a121-f99520cc6b1d

I'll agree with the others and discourage trying to do this in a day, especially over a holiday period when it's likely to be even more of a zoo than usual, trains will likely be packed like sardines, and a private driver would be NO help at all as you can't drive within most of the villages.

There is also no singular hike (as in "the hike.") The CT park region is made of many trails, lots of them heading up into the hills and are longer and more strenuous than the SVA2 "Blue Trail" route most people think is the only hike in the system. That route is the most popular but 2 of the 4 legs have been closed for years and look to remain closed in 2020. Monterosso> Vernazza and Vernazza > Corniglia sections (currently closed) are usually open during high and shoulder seasons: Corniglia>Manarola and Manaola> Riomaggiore will not be. Park passes are required for hiking either or both of the first two legs if they're open.

http://www.parconazionale5terre.it/Eindex.php
http://www.parconazionale5terre.it/Esentieri-outdoor.php

Still, weather could also be a crapshoot: spring rain or rockfall threats can abruptly close the trail systems or they may close to damage from previous heavy storms. All-in-all, it's not a great destination when it's wet.

Need advice on going to Cinque terre for the day. Will be in Florence April 11 and 12. (Easter Sunday) Is this reasonable?

No. How long will you be in Florence? It reads you'll be in Florence for just two days. You don't want to waste a day on any day trip. Two days in Florence will just be enough time to skim the surface of this magical city.

As mentioned you would be there when it is at its busiest. See this. Think Disney World at its worst.

To get there early in the morning you need to take the FrecciaBianca
high speed train that departs from the Firenze Campo di Marte station
at around 07:30

Just to add to Roberto's helpful advice, the train he's referring to departs April 12th from Firenze Campo di Martre station to La Spezia Centrale at 7:54, and takes 1 hr, 43 minutes. There's another making return trip at 19:44 that takes 1 hr, 45 minutes. There are the only trains that cover ground between the two cities that quickly, and they likely run every day. In La Spezia, you'd change to local trains to get around the region.

That aside, there's no way I'd try to do this trip during Easter Weekend.
One little issue with the article containing the good info about crowds is that's from 2016 and mentions "plans to restrict tourists" that didn't get sorted out. So for anyone using this thread for their own research, there are currently no restrictions on number of visitors entering the CT in 2020. I'll also raise an eyebrow that, "There isn’t even an escape on the famed hiking trails that connect the villages...an endless procession of often ill-shod, panting and poorly-prepared people." While more true than not of the "Blue" route, hikers are finding breathing room on others of the trails. See the post by Andrew H on this thread from last spring:

https://community.ricksteves.com/travel-forum/italy/cinque-terre-hiking-conditions

tm,

While a day trip to the Cinque Terre is certainly possible, I tend to agree with the others that Easter Sunday is perhaps not the best time, and the trip may not be entirely enjoyable. Of course, you could take your chances and hope for the best. It would probably be wise to check the cruise ship schedules for Livorno and La Spezia prior to making the trip.

Which "hike" are you referring to? If you're planning to hike the popular Sentiero Azzurro trails, note that two of the four segments are currently closed and will likely remain so this year. The status of the trails can change on short notice due to storm damage or whatever, but the Monterosso - Vernazza - Corniglia segments should be open. Note that a Park Pass is required to hike those. The pass can be easily bought when you get there. If you hike those segments, it will only take about 3 hours.

I haven't found that they "often change schedules and cancel trains". If there are huge crowds, the trains can be delayed. Depending on which train you choose, there may be one of more changes, perhaps in La Spezia or Pisa Centrale.

Good luck with your decision!

Agreeing with Doug. If you only have 2 days in Florence, then stick with Florence. If Florence is not a place that intrigues you, then go to CT for those 2 days and don't bother with Florence at all. Note, I have done Florence twice (2019 and 2017) and loved it both times. Did CT in 2017 and loved it as well. One day in each does neither justice.....

Will be in Florence April 11 and 12

Oh gosh, I didn't completely digest this. If you're there for such a short amount of time, then just stay there. Florence offers all sort of riches that are well worth exploring. If they don't appeal, I'd question the decision to stay there to begin with!

I did not notice that either. 2 days in Florence? Just stay there.

Oops, I missed the two day time frame in Florence too. I agree that the OP's time would be better spent in Florence. If the plan is to stay two nights there, that's only a day and a bit for actual touring in Florence.

Train schedules have changed, the 7:28 is now the 7:54 arriving at 10:41. If you take the 16:45 back to SM Novella, arriving at 20:07 with the intention of having dinner closer to 21:00, for 5.5 or so hours in the village[s] you will spend 8 hours on trains and going to and from stations.

16:45 back to SM Novella, arriving at 20:07....

I'm not even seeing this train on the Trenitalia website but no need to take one that will take over three hours back to Florence. As mentioned above, there is a 19:44 train from La Spezia to Firenze Campo di Martre, that takes just 1 hr, 45 minutes, or 2 hrs, 6 minutes to S.M. Novella (change at Campo di Martre).

There is also a 16:16 train from La Spezia Centrale that arrives at SM Novella in 1 hour, 45 minutes with a change in Pisa. There are others that make the trip in slightly over two hours/1 train change as well.

So, the rail process to and from Florence doesn't need to eat 8 hours but again, not that any of us are recommending this trip over Easter Weekend! :O)

I no longer can recommend CT due to overcrowding. I cannot imagine what the trains would be like on a holiday weekend. I agree, if you are two days in Florence, stay in Florence. But if you are looking to box-tick/bucket list, then try Pisa or Lucca. However, if you insist on going, try training Riomaggiore then take the water taxi/ferry up the coast to Monterosso with stops along the way and then catch your train back from there.

How is Cinque Terre early October our plan is to go weather depending. We are from the Pacific Northwest so rain doesn’t bother us. But are the towns shut down when it rains? We will be there and doing a day trip from Florence. I hear a lot people talk about how crowded it is and wondering if we should go to Pisa or Lucca instead

The towns don't "shut down" in rain. Trails, however, are not safe when wet so they usually do.

How busy the CT may be might depend on how large and/or how many ships are in port in La Spezia on the day you go but October is said to be one of the best months to visit.

https://www.apathtolunch.com/2016/03/cinque-terre-16-tips-for-avoiding-crowds.html

I haven't been to the Cinque Terra, but I don't understand why anyone would do a day trip from any city if they are only there two days. Too much travel in too short of a time.

Naturally, Italian rain is more complicated. There are now sophisticated weather alerts issued for 5 zones in Liguria to avoid the dangers of flash flooding in steep terrain and flooding from overflowing streams and rivers. They are rated yellow, orange and red for possibly bad, likely bad, and surely bad. They were implemented (or more broadly disseminated) about 3 years ago, and there were many this fall - about 8 in the 5 weeks we were there. When orange & red are in effect the paid CT trails are closed, and hiking is not advised otherwise. Schools are also closed for orange & red and guides are not supposed to bring groups into the CT (widely ignored, it seems). This is the FAQ on this from the National Park of the Cinque Terre:

16) When it rains, are the paths walkable?
In case of rain the trails of the Cinque Terre become particularly slippery and difficult to walk down even for people with good hiking practice. In case of bad weather, the Park Authority advises against taking any type of excursion.
In the event of a Yellow, Orange and Red alert state declared by the Civil Protection Service of the Liguria Region, self-protection measures are actived according to the the civil protection plans of the municipalities of Riomaggiore, Vernazza and Monterosso.
In the event of Orange and Red alert state, the Park Authority interrupts the sale of Cinque Terrre Card, keeping the information points at the entrance of the SVA trail from Corniglia to Vernazza and from Vernazza to Monterosso.