The long Memorial Day weekend is typically the unofficial kick-off for summer. From the Jersey shore to Los Angeles, beaches are parks are starting to reopen. Many people who have been quarantining indoors for months might be eager to get to the beach or park.

"I feel for people wanting to get outside," Dr. Russell Buhr, assistant professor of medicine at UCLA Health who practices pulmonary and critical care medicine, and studies Covid-19, tells CNBC Make It.

Broadly speaking, being outdoors is safer than being inside, because there's more airflow and room to physically distance. But that doesn't mean that you can relax the important Covid-19 prevention measures that are meant to stop the spread.

"We have a responsibility to each other, and nobody wants to be the weakest link," Dr. Iahn Gonsenhauser, chief quality and patient safety officer at The Ohio State University Wexner Medical Center, tells CNBC Make It.

"Consider how we approach things in a civil and respectful manner," Gonsenhauser says. "That's the reason that we're choosing to wear a mask and continue safe social distancing: it's not because anybody's telling us we have to, it's because it's the right thing to do."

Here are the things to avoid when you're enjoying the long weekend, according to experts and the Centers for Disease Control and Prevention.

Don't go to the public pool

The CDC says that there's no evidence that Covid-19 can be spread through the water in hot tubs, pools and water play areas. The chemicals chlorine and bromine used in pools have been shown to kill other types of coronaviruses.

But avoid a public pools with lots of people and high-touch surfaces surrounding the water and locker rooms, Gonsenhauser says. Parents should keep in mind whether their children are even capable of staying at least six feet from others before you go to a public pool or swimming area, per the CDC.

Natural bodies of water, such as the ocean, lakes and rivers, may be large enough to dilute the virus and decrease the risk. However, you should keep your distance from other people swimming and do your best not to accidentally swallow the water. As with on-land, you should avoid gatherings of more than 10 people and continue to wash your hands frequently, according to the CDC.

"Swimming in a pool in a friend or neighbor's backyard, maintaining space apart while you're enjoying water is lower risk than going to a public swimming pool," Buhr says.

… or a playground

Playgrounds are off-limits for a few reasons: it's tough to keep them disinfected and they're typically crowded with kids who can easily become infected after touching something contaminated, according to the CDC. Many playgrounds around the country are closed to the public, but it's important to follow those measures and find safer ways to play.

Don't sit in one spot all day

"Beaches are meant to be enjoyed for active recreation currently," Buhr says. "So, that means going outside and taking a stroll, riding your bike, going for a swim in the ocean — all of those things are perfectly fine."

Setting up a tent and a barbecue, or sitting on the beach in one place for a long period of time is not a good idea, and in some places, it may not be allowed, Buhr says. "The reason for that is, the closer that people are together, the more their risk is of transmission," he says. If your plan is to go and stay in one spot all day, you may be asked to move along by the local authorities.

Don't play group sports

While getting together for a pick-up game of softball or beach volleyball might be your usual summer routine, team sports are not recommended during the pandemic, according to the CDC. Getting together with a group of people outside of your home and sharing high-touch equipment increases your risk of infection.

Sports like golfing, biking and running tend to be safer, because they can be done outside and from a distance. Stick to exercising with someone in your home, wear a mask, wash your hands and be careful to get keep that space between you and the other parties, Buhr says.

Don't forget to wear a mask

Even in the summer heat, it's important to wear a mask or cloth face covering anytime you're interacting with people outside of your home, even if you're outdoors, Buhr says. The whole point of wearing a mask is to capture respiratory droplets that might be carrying the virus from spreading to others, he says.

"The mask isn't about protecting yourself as much it is about protecting everyone else," he says.

If you're in the water, then wearing a mask or cloth face covering can make it difficult to breathe, per the CDC. You should still bring a mask to the beach to wear when you're on dry land but remove it when you swim.

Don't share food or drinks

Outdoor BBQs are still risky, especially if you're sharing food with people who live outside of your home, Buhr says.

"If you're grilling out together, and everybody grabs their burger off the grill and takes it on their own individual plate, and goes and eats it on their own, that risk is pretty low," he says. However, if you have communal dishes of food sitting out that people may be touching, breathing on and returning to often throughout the event, then the risk of infection is higher.

The safest option would be to have a cookout with people you're quarantining with, or bring your own food and stay a minimum of six feet away from people outside.  

Don't travel to a beach or park far away

If you're headed to a new community, whether it's an hour away or across the country, "there's always the concern that you could be putting others in that community at risk by bringing virus with you," Buhr says. It's important to be respectful, and follow precautions such as wearing a mask and maintaining physical distance from others around you.

"We do have to keep reminding ourselves: It's not just about the risk for yourself, it's about the risk to others around you, and minimizing the spread of an infection through the community to protect those who maybe are not as healthy as you," he says.

Don't venture out if you're sick

You've heard this for months, but it bears repeating: Stay home when you are sick. If you have symptoms of Covid-19, such as a fever or cough, or have been exposed to the virus in the last 14 days, you shouldn't be in public, and that includes parks, according to the CDC.

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