(CNN) Weeks ago, as President Donald Trump warned that ICE agents were preparing raids across the country , a 41-year-old housekeeper and babysitter in Miami headed to the grocery store with her daughter.

They knew they'd be staying inside and needed to stock up on supplies.

"I felt that day like it was a hurricane coming," the undocumented immigrant from Nicaragua told CNN.

Since then, the raids Trump threatened haven't happened . But for millions of undocumented immigrants living across the United States, the storm is still brewing.

With a new threat of immigration raids on Sunday , immigrant rights advocates and undocumented immigrants told CNN that fear in their communities is growing.

And undocumented immigrants are bracing themselves.

They're calling hotlines, afraid to go outside and unsure of where to turn. Some are staying home from work. Others are posting signs by doors inside their homes telling them what to do if ICE agents show up.

She woke up last night, screaming

While the uneasy mix of panic and preparation weeks ago felt like a hurricane, there was one notable difference for the housekeeper in Miami. The store in her neighborhood seemed eerily empty. Already, she said, people were afraid to go out.

She returned home with a plan.

"I said, 'OK, you know what, we're going to keep the windows down, the blinds down. I don't want any noise. I want everybody to stay calm and try to turn off the lights in the living room, so if they come, they don't know that we are in the house,'" she said. "I know my rights. I know that I don't have to open the door. I know a lot of things, but even with that it's really scary."

The woman shared her story with CNN but asked to be identified only by a pseudonym, Elena, out of fear she could face repercussions for speaking out. She said she came to the United States more than two decades ago on a visa, which she overstayed as she sought asylum.

Elena lost her case but stayed in the United States, where she says she's built a life and grown her family. She's terrified of being separated from them.

"This is a horrible feeling," she said Thursday. "These past two days, I've been waking up in the middle of the night. My husband says, 'What happened to you last night? You started screaming in your dream.'"

A man is detained by Immigration and Customs Enforcement agents on October 14, 2015, in Los Angeles, California.

Frightened farm workers are staying home

Élfido García sat in the scorching sun Thursday tending to agave plants in Homestead, Florida. For weeks, he's been picking up extra work to fill in for colleagues who he says are too scared to leave home after hearing about the possibility of raids on TV.

The migrant worker from Guatemala says he only leaves home to walk to work, knowing that along the way he risks the possibility of arrest by authorities.

"Yes, I'm taking the risk," he said, "but just to fight for my family."

As the threat of immigration raids looms in South Florida, fields once filled with workers look empty. Weeds are popping up where crops once grew. And the number of "help wanted" signs posted offering work are on the rise.

A growing number of workers are scared to leave their homes, leaving farm owners in search of laborers to harvest their crops.

Farm owner Gustavo Serna told CNN en Español that crops are being lost as a result.

"Because of the lack of workers, many times people are losing up to 50% of their harvest," he said.

Across the country, in Worthington, Minnesota, an undocumented agriculture worker who spoke with CNN said the community there is terrified, too. He said he's planning to hunker down all weekend until he is certain ICE agents aren't in the streets.

"I don't want to leave my family devastated," he said, "so we are just going to stay inside."

Élfido García says he's been hunkering down at home as reports of possible immigration raids resurface. He only leaves to walk to work.

Questions and frantic calls

Advocates note that fears of deportation are familiar in immigrant communities across the country. And this isn't the first time raids have been threatened or reported on before they occur.

But this time around, many advocates say the concerns they're hearing from immigrants are more intense.

"There is a lot of panic and a lot of fear, even though we know that these raids happen every year. ... Something feels tangibly different this time around," said Nayim Islam, an immigrant rights organizer for Desis Rising Up & Moving, an advocacy group that works with South Asian and Indo-Caribbean communities in New York City.

Many groups have set up hotlines for community members to report raids and reach out for help.

"We got a call from a mom who said that her little girl wasn't feeling well and she was afraid to go to the doctor. She was trying to figure out how to make it there," said Melissa Taveras, a spokeswoman for the Florida Immigrant Coalition.

"We keep getting calls and messages from folks, saying, 'We're scared. What should we do?'" Taveras said. "I've seen those sorts of messages and calls more than usual, which really worries me, because those are people that are preparing in fear."

Across the country, advocacy groups have been hosting "Know Your Rights" trainings and circulating fliers and social medial posts with guidelines about what they say immigrants should do if ICE agents show up at their door.

The word seems to have gotten out, said Abel Nuñez, executive director of the Central American Resource Center in Washington.

"A lot of people have heard that message," he said. "I think the question is, if it does happen to them, are they going to implement it? It's one thing for me to give you a card or a paper with your rights. It's another thing at five in the morning, when you hear a loud knock at your door and someone's yelling, ' Police!' Are you going to let them in? That's a very different environment.

"At this point, it's just about repetition, reminding them of what they have, so that it's muscle memory."

'This is not a life'

Now that another ICE operation appears to be imminent, Elena says she doesn't want to risk staying home to find out what would happen if federal agents show up at her door.

"This week we're planning to move out for a week until this stops, but next month we're going to move from the apartment," she said. "I've been in that apartment for five years now, so I don't think it's secure."

Fear, she says, has become a constant. She's so exhausted that sometimes she wishes she could go back to Nicaragua.

But she says recent unrest there has made her scared to return to the country she left decades ago.

"Sometimes I feel that way. I want to say...'I give up. I'm going back.' Because this is not a life. ... I'm driving. I have no driver's license.

"My daughter sometimes says, 'Mom, I'm scared you're not going to come back home,'" Elena says. "I don't know if I'm going to get the opportunity to feel that I have a free life, that I live in peace."