 -- True bellwether counties in U.S. presidential elections are hard to find. Elections often depend on turnout in partisan strongholds and on keeping those margins bigger or smaller than the last time around.

Still, some counties can tell us which way the wind is blowing. Either by demographic makeup or by clear-cut targets based on past results, they can foreshadow what will happen in the rest of the country. In that spirit, here are a few counties worth keeping an eye on as the first results come in tonight for the eastern half of the U.S.

1. Miami-Dade, Florida. (8 p.m. E.T.) Nationwide, it's second only to Los Angeles in Hispanic population, with 581,000 (35.7 percent, according to the Pew Research Center), and as such, Miami-Dade could give an early indication whether we'll see a Hispanic surge tonight in places like Nevada and Colorado. Barack Obama won this county twice, with 57 percent in 2008 and 61 percent in 2012, so look for Hillary Clinton to top the low 60s if that surge materializes.

It could forecast the winner of Florida — one of two true Eastern tossup states, along with North Carolina, that will be critical as the night progresses.

Florida's 24 percent Hispanic population has translated to just 15.7 percent of registered voters, according to the state's latest statistics, but some of its most important counties have seen the highest growth in Hispanic registration. Clinton will look for totals in the 60 percent range in Osceola, Broward (Fort Lauderdale) and Orange (Orlando), all of which saw the Hispanic registration share grow by 2 to 5 percent since 2012. Sparsely populated Hendry, in central southern Florida, voted 52.3 percent for Romney in 2012 and saw Hispanic registration rise by 5.8 percent. A flip could be a good sign for Clinton.

2. Wake County, North Carolina. (7:30 p.m. E.T.) Home to Raleigh, it's the biggest county in critical North Carolina, and its demographics will test Donald Trump's appeal to college-educated suburban voters and Clinton's to African-Americans: Wake is 20.1 percent percent black by registration, and it's the second-most-educated county in the state, with 48.3 percent of residents 25 or older having college degrees.

Clinton will want to hit the high 50s there to stay competitive, and she held a midnight rally there on the eve of Election Day to that end. Wake broke for Obama in 2008 (57.1 percent), but his support dropped off in 2012 (54.5 percent) as he lost the state in his second run. Clinton and Ted Cruz won the primaries there.

Elsewhere in North Carolina, look to tiny 92.5 percent white Watauga on the Tennessee border, which has voted for the statewide presidential winner since 1996. Durham will be a good indicator of African-American turnout for Clinton: It's 37 percent African-American by registration, and Clinton will need 76 percent there if she wants to top Obama's 2012 total.

3. Cobb County, Georgia. (7 p.m. E.T.) This county in the northwestern Atlanta area is one of Georgia's biggest and most educated counties. It'll be another test of Trump's appeal to college-educated whites. Democrats have dominated the heart of Atlanta (Fulton County), but Romney carried Cobb with 55 percent in 2012, and Democrat Michelle Nunn took only 42 percent in Cobb in the 2014 Senate race. Trump will need at least in the mid-50s there, and if Clinton makes it close, this could be a canary in the coal mine.

4. Franklin County, Ohio. (7:30 p.m. E.T.) Home to Columbus, it gave Mitt Romney the most votes of any Ohio county in 2012 (although Obama won it with 60.1 percent). But Franklin was the strongest John Kasich county in the U.S. in the 2016 primaries, according to this New York Times map. Kasich took 63.7 percent there, feeding voters a steady diet of anti-Trump cautioning. Franklin might say something about whether Republicans are behind their candidate, and Trump will want to keep Clinton under 60 percent there.

5. Wayne County, Michigan. (9 p.m. E.T.) Home to Detroit. If Clinton has an enthusiasm problem in the Democratic base, it could show there. Obama carried it with 74 percent in 2008 and 72 percent in 2012, but unemployment has remained relatively high at 6.5 percent in Wayne County, with Michigan among the states hit hardest by the recession during Obama's presidency. Polls have shown Clinton ahead in Michigan, but Democratic enthusiasm in Detroit could be key. Obama, Bill Clinton and Hillary Clinton all campaigned in Michigan on Monday, suggesting a campaign that sees Michigan turnout as important to its chances.

Rural bonus: Florida Panhandle. (8 p.m. E.T.) How fired up is the deep-red base? Santa Rosa, Okaloosa, Washington, Bay: Romney took about 70 percent in these small Panhandle counties in 2012. Will Trump bank extra votes there in 2012? North Carolina's Bernie country. (7:30 p.m. ET) Western North Carolina felt the Bern. Buncombe County (Asheville) backed Obama (55 percent) against Romney in 2012, but Bernie Sanders crushed Clinton in the primary there, taking 62 percent to her 35 percent. A loss for Clinton in Buncombe could mean she failed to rally the Demoratic Party's Bernie wing.