Forests set ablaze (or afire) by lightning.    From Wordnet, Princeton University. 

BIGGS -- "I hear the jail was afire this morning?".    From Wordnik.com.  [The New Pun Book] Reference

His voice felt like long strands of spaghetti set afire.    From Wordnik.com.  [Faithless] Reference

"Quick, and do something, or the whole town will be afire!".    From Wordnik.com.  [The Young Railroaders Tales of Adventure and Ingenuity] Reference

An 'I don't believe you ever set that shed afire on purpose.    From Wordnik.com.  [A Campfire Girl's First Council Fire The Camp Fire Girls In the Woods] Reference

"Let me set your heart afire with burning kisses," he murmured.    From Wordnik.com.  [Bandit Love] Reference

Took everything they found, but they didn't set de house afire.    From Wordnik.com.  [Slave Narratives: a Folk History of Slavery in the United States From Interviews with Former Slaves South Carolina Narratives, Part 4] Reference

In a few moments the bundle of brush was afire and in the chimney.    From Wordnik.com.  [The Ranger Boys and the Border Smugglers] Reference

Is a house afire or a friend ill; or does a feast wait till you come?.    From Wordnik.com.  [The Story-teller] Reference

Now rearrange these nearly meaningless syllables: "My house is afire.".    From Wordnik.com.  [The Principles of English Versification] Reference

A match or small piece of wood is lighted and when well afire blown out.    From Wordnik.com.  [Games For All Occasions] Reference

Once you get this beastly place afire, I will manage to make my way out.    From Wordnik.com.  [Madge Morton's Secret] Reference

He turned and fired without stopping, setting the thing afire in midair.    From Wordnik.com.  [Deathworld] Reference

He came back into the office about eight o'clock all afire with his story.    From Wordnik.com.  [How to Write Letters (Formerly The Book of Letters) A Complete Guide to Correct Business and Personal Correspondence] Reference

You dropped them in my boat the other night when you tried to set it afire.    From Wordnik.com.  [Tom Swift and His Motor-Boat, or, the Rivals of Lake Carlopa] Reference

You may not set the world afire with your fame but you'll be worth hearing.    From Wordnik.com.  [Patchwork A Story of 'The Plain People'] Reference

Looking towards the Hun trenches it appeared as if the whole line was afire.    From Wordnik.com.  [Over the top with the 25th Chronicle of events at Vimy Ridge and Courcellette] Reference

"It is I," said the sun; "come and set me free, before the whole earth is afire.".    From Wordnik.com.  [How to Tell Stories to Children, And Some Stories to Tell] Reference

 Why is it nobody else is home nearly every time the chimney sets the roof afire?.    From Wordnik.com.  [Failure] Reference

"Maw'll just about skin you alive for that when I tell her you set the shed afire!".    From Wordnik.com.  [A Campfire Girl's First Council Fire The Camp Fire Girls In the Woods] Reference

Some of those escaped with hair and clothes afire, diving into snowdrifts for relief.    From Wordnik.com.  [The Night The Music Died] Reference

My bolts set afire inconspicuous shrubs of lowlands and I have felled towering trees.    From Wordnik.com.  [NATURAE] Reference

Mixy was there on the back porch, I noticed, lapping away at her milk like a house afire.    From Wordnik.com.  [Shenanigans at Sugar Creek] Reference

"They start off like a house afire, but about the fifth inning they begin to crumple up.".    From Wordnik.com.  [Baseball Joe Around the World Pitching on a Grand Tour] Reference

We never set the barn afire, and you can't prove that we did, 'said one rather anxiously.    From Wordnik.com.  [Sarah's School Friend] Reference

"Hold on! what's that he's saying now about somebody setting his store afire on purpose?".    From Wordnik.com.  [The Banner Boy Scouts Snowbound A Tour on Skates and Iceboats] Reference

Day by day the sun's rays grew more intense until it seemed they must set the world afire.    From Wordnik.com.  [The Black Phantom] Reference

The rest of the livestock was turned from the corrals and the cabin and stables set afire.    From Wordnik.com.  [David Lannarck, Midget An Adventure Story] Reference

A swamp on the place was afire and the fire coming through that long swamp grass very rapidly.    From Wordnik.com.  [Old Rail Fence Corners The A. B. C's. of Minnesota History] Reference

The flash-light set fire to a lace curtain and before any one could stop it the house was afire.    From Wordnik.com.  [Newspaper Reporting and Correspondence A Manual for Reporters, Correspondents, and Students of Newspaper Writing] Reference

The wooden shelves were afire, the flames feeding on the powdered spices that floated in the air.    From Wordnik.com.  [The Saracen: Land of the Infidel] Reference

Mr. Rugg also informed Mr. Bobbsey how the boathouse had been set afire, and expressed his sorrow.    From Wordnik.com.  [The Bobbsey Twins at School] Reference

"He sure started out like a house afire, sir, but he seems to be fallin 'down now," Murk declared.    From Wordnik.com.  [The Brand of Silence A Detective Story] Reference

We are as unsafe as though we were on a wandering star, or meteor -- only this island is not afire.    From Wordnik.com.  [On a Torn-Away World Or, the Captives of the Great Earthquake] Reference

"I bet they never got up this early before unless their house was afire," Ethel Zimmerman ventured.    From Wordnik.com.  [Campfire Girls at Twin Lakes The Quest of a Summer Vacation] Reference