The summer travel season is in full swing, and you might be planning to set up your own "out of office" message soon.

But in the U.S., which has a culture of overworking and zero national laws that guarantee paid vacation time, people have a hard time taking the days off they're given. The average American leaves 9½ vacation days on the table each year, and when they do take time off, a majority say they're unable to stop working.

The temptation to check work messages on vacation is even difficult for Lene Vindenes, 28, who lives in Oslo, Norway, and works as a social media manager. Like many European workers, she's entitled to a generous amount of paid leave by law.

Her company guarantees 25 paid vacation days per year, and she's required to take three weeks of vacation during the summer between June and August. She once took off for four weeks to travel around Europe.

She admits it's "really hard" to not check email when she's off the clock, and coming back from weeks away is "always overwhelming."

Here are her four top tips for how she prepares to be OOO.

1. Ask your clients what they need from you

Just as you'd let your boss and team know when you're going to be away, Vindenes says it's customary for her to send an email to people she works closely with about her vacation plans. She starts this process a month ahead of her scheduled time off.

"I usually start with informing my clients that I will take time off, and ask them if they have any upcoming projects I need to be aware of," she says.

It's helpful for her to know what her clients' priorities are, and then figure out what she can complete before she's out, what other colleagues can do while she's away, and what can wait until she's back.

2. Prepare a coworker coverage plan

Vindenes says the thing that puts her most at ease before vacation is knowing "both the company and my colleagues have my back."

She and her team have "very clear routines" to keep everything running smoothly while anyone is away and with the common understanding that "in Norway, we do have respect for each other's time off and don't really want to contact the person unless there is an emergency."

A week before her vacation, Vindenes will prepare handover materials for colleagues on things that are in progress "so they are well informed and can easily jump in when needed."

3. Let your boss know where things are

Finally, as she gets closer to being out of office, Vindenes will give her boss a status update on projects.

This way he can provide any insights about how to prioritize the remainder of her time before PTO, or can step in and help out if needed.

Vindenes makes sure to have a clear and realistic plan for wrapping things up before she's away. "It's hard to take vacation when you have unfinished projects, so for my own sake, I finish as much as I can so I can step into my vacation with a good conscience. "

4. Set your out-of-office and turn off all notifications

A few weeks of prep work pays off, Vindenes says: "It's important that everyone around me — clients, colleagues and managers — are well informed. This minimizes the chances of them having to contact me," she says. "I also try to have a clear 'out of office' auto-reply, which makes it easy for my clients to know who they can contact in my absence."

Then, she'll turn off notifications on her email, messaging and other work-related apps.

Beyond the to-dos, Vindenes says it's helpful to work in an environment that encourages taking time off.

"I also am very aware that I am not a brain surgeon," she says. "I do marketing. Nobody will die."

After a vacation, Vindenes will ask colleagues to help her catch up on what she missed, and she'll make a to-do list prioritized by urgency to "feel more organized and less overwhelmed when going through 500 emails."

The European vacation mentality

Overall, Vindenes finds it "fascinating" that Europeans have a different perspective from Americans on work-life balance and the value of vacation time.

"In my opinion, there is so much more to experience outside of work, and I do not want my work to become my personality," she says. While she's "definitely not the best at putting work and stress aside," she says that it helps "to have people around me that remind me that work is not everything."

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Check out: Americans living in Europe on how easy it is to take PTO: ‘I am still getting used to 30 days of vacation’