Americans are once again opening their wallets to support those in need, this time for people suffering from the devastation caused by the wildfires in California.

If you want to make a contribution, there are a number of charities you can consider that have been evaluated by two charity watchdogs, Charity Navigator, and CharityWatch. They evaluate charities on many factors, including how much donated money is used for their charitable programs rather than fundraising and general expenses. Here are five that have been recommended:

Direct Relief is an international medical-relief organization based in Goleta, Calif. It is distributing particulate masks to aid those who have asthma and other medical conditions made worse by the smoke and ash caused by the California wildfires, says Damon Taugher, the group's director of U.S. programs. Direct Relief has already given out more than 100,000 masks. It is also distributing medication to people forced to flee their homes and move to shelters.

The Jewish Community Federation of San Francisco, the Peninsula, Marin and Sonoma Counties, headquartered in San Francisco, is working with local synagogues to help provide food and shelter for those who have lost their homes. It has also set up the North Bay Emergency Fund to raise money.

Two other top-rated groups are also helping: the American Red Cross, which is operating evacuation shelters, and Episcopal Relief & Development, which is partnering with the Episcopal Diocese of Northern California to provide food, housing, and a place to store personal items, among other things.

Another charity, the Sonoma Humane Society based in Santa Rosa, Calif., is taking in stray pets, giving first aid to animals that have been burned or otherwise affected by the fires, and providing pet food and other supplies to evacuation shelters that are taking in owners and their pets, says Melissa Dobar, the group's development director.

"We are anticipating a large influx of injured animals," Dobar says.

More on Charitable Giving

If you're considering giving to a group that hasn't been evaluated by a watchdog, you should check its financial statements, annual report, and other information about how it spends money before making a donation, says Bennett Weiner, chief operating officer of the BBB Wise Giving Alliance, another charity watchdog.

According to the alliance, at least 65 percent of a nonprofit's spending should be used for its programs as opposed to fundraising or administrative expenses.

You can find that information in a charity's nonprofit tax return—the so-called Form 990—which you can often access on a charity's website. Financial information is also available at GuideStar, a national database of nonprofits. (Free registration is required.) 

When you look at the tax return you'll see lots of details, including how much a group pays its top officials. 

If you want to give locally, it's generally a safe bet to donate to a United Way or a community foundation or fundraising campaign that has oversight by an attorney, bank, or other authority that can make sure the money is used properly, Weiner says.

United Way of the Wine Country in Santa Rosa has set up a fund to help raise money for short-term aid to victims, says its CEO, Michael Kallhoff. Another option is the San Jose-based United Way of the Bay Area, which has created a fund for long-term needs, such as rebuilding homes. The Latino Community Foundation is raising funds mostly for helping farmworker communities, among others.

Tips for Making Effective Donations

Before making a donation, review these suggestions so that your gift will count as much as possible.

Find out whether the charity you're considering is helping in California. Even if a charity has a top rating from a watchdog, it may not be involved with the California wildfire relief efforts. Call the organization or check its website to find out. 

Donate money. This is generally better than giving supplies or other items that must be shipped to the disaster location, Weiner says. Charities helping on the ground are in a good position to know what's needed, he adds.

Give for the long term. The effects of disasters such as the California wildfires can go on for months or years, notes Daniel Borochoff, founder of CharityWatch. So consider making additional contributions later on.

Beware of unsolicited appeals. Don't blindly respond to charity appeals that show up in an email or text from someone you don't know. It may be a scam, says Borochoff. 

Use crowdfunding websites cautiously. While you can turn to a site such as GoFundMe or GiveForward to make donations to people you know, Borochoff says that with others, it can be difficult to know whether a fundraising campaign is legitimate and whether the money will be used as represented.

Also keep in mind that crowdfunding websites usually take a small percentage of every donation and charge a separate processing fee. Note that donations to individuals typically aren't tax deductible.