venice to Cinque Terre

It's because you have to switch to a local or Regionale train to get to the CT villages, and those schedules are often only posted a week in advance. Find out what day of the week August 1st is, then pick that same day of the week next week to plug into the dates on trenitalia.com. It's weird. Happy travels.

from Venice to Monterosso there are a few options all with at least one connection, some with multiple connections duration is just under 5 hours to just over 6 hours
it may be too early for Aug 1 schedule but you can look on trenitalia website for train times for an earlier date to get an idea

Train schedules are just for the upcoming 60 days. With all the political/euro problems, government subsidized travel is subject to change at any time. In other words, you cannot set your exact schedule right now. Did you get the message that much of Italy shuts down for August? They go on vacation due to it being so hot of a climate for the whole month. Don't consider going to the C/T unless you had a confirmed hotel reservation. If you can change your travel schedule, the best months are April/May, September/October. Flights are also much cheaper then, and the crowds far fewer. To get from Venice, you'd take a train through Bologna to Florence. You'll change trains for an hour train trip to Pisa. You'll change trains going northwest to LaSpezia. There, you'll get on a slow regional train that stops at every little "burg" running up the cost, to the 4 towns of the Cinque Terre. It's a 7 hour trip all day trip most times. You can look up all European travel on Mapquest's maps and move the map larger and smaller with the + and -. You move back and forth with the arrrows following your intended routes.

kristen, Unless there's a Sciopero on the day you'll be travelling, you won't have any problems getting from Venice to Monterosso. The schedules for Augsust won't be posted yet, so do a search for a day within the next few weeks, on the same day-of-the-week that you'll be travelling. According to current schedules, there are two possible routings on that particular trip. For departures from Venezia Santa Lucia to Monterosso, you'll either travel via Milano Centrale OR via Firenze and La Spezia Migliarina. The shortest time I could find was 5H:49M and current second class fare was €55.50. As the others have mentioned, many Italians close their businesses and take holidays in August, however some will remain open. Although I haven't been there in August, I very much doubt that anyone in the Cinque Terre will be closing then, especially this year. Closing in the middle of tourist season when they need as much revenue as possible to rebuild their lives and businesses would NOT be a good business decision! I would also highly recommend that you book accommodations in Monterosso VERY SOON, as August will be busy. Happy travels!