After millions of Americans in the path of totality look up for the solar eclipse on Monday, prepare to look down: A rare, double brood of cicadas is set to emerge in a few weeks.

Two different groups, or broods, of cicadas will emerge across multiple states this year, for the first such emergence in 221 years. The 13-year Brood XIX will emerge in 14 states across the Southeast and Midwest, and the 17-year Brood XIII will emerge in five Midwestern states around the same time according to Cicada Mania.

And like the solar eclipse, which isn't expected to be seen in the contiguous U.S. until 2044, the next cicada double-emergence of these two broods won't happen again for a while, next predicted in 2245.

Here's what to know about the two cicada broods emerging this year.

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When are the cicadas emerging?

Both Brood XIX (19) and Brood XIII are estimated to emerge beginning in mid-May and lasting through late June. The two broods will begin to emerge when the soil 8 inches underground reaches 64 degrees, and are often triggered by a warm rain.

What are Brood XIX cicadas?

Brood XIX (19) is estimated to emerge in these states beginning mid-May and lasting through late June, according to Cicada Mania:

• Alabama.
• Arkansas.
• Georgia.
• Illinois.
• Indiana.
• Kentucky.
• Louisiana.
• Mississippi.
• Missouri.
• North Carolina.
• Oklahoma.
• South Carolina.
• Tennessee.
• Virginia.

The brood last emerged in 2011, and has a 13-year life cycle.

What are Brood XIII cicadas?

Brood XIII (13) will emerge these states in mid-May and ending in late June:

• Illinois.
• Indiana.
• Iowa.
• Wisconsin.

The brood may also appear in Michigan, Cicada Mania says.

Unlike the other brood, these cicadas have a 17-year life cycle, and last emerged in 2007.