1. Italian earth quake

A deadly earthquake rocked central Italy overnight. An unknown number of people are trapped beneath rubble and at least 21 have died, according to CNN affiliate Rai.

The quake seemed to subdue the mood in early European trading, but most regional indexes are now moving higher, and Italy's main market is trading up 0.5%. Insurance firm Generali has fully recovered after taking a 1% hit.

Asian markets are mixed as they close out the day. U.S. stock futures are little changed.

2. Stocks to watch

Shares in advertising group WPP (WPPGY) shot up to their highest levels ever in London trading, surging by just over 5% as investors cheered the company's earnings. WPP also trades on the Nasdaq in New York.

Intuit (INTU) shares are falling by about 5% in extended trading as investors reacted with disappointment to its earnings.

Tesla (TSLA) stock could see higher-than-normal volumes Wednesday after it unveiled a new battery that it says will allow its Model S to go from 0 to 60 mph in 2.5 seconds, making it the fastest production car in the world.

3. Dollar edges higher

The dollar edged forward against major rivals on Wednesday, while waiting for the Jackson Hole speech.

Hawkish comments by Fed officials, most recently vice chair Stanley Fischer, raised speculation that Yellen could reveal a more optimistic outlook, dampening her generally dovish stance and leaving the door open to a possible rate hike in September.

The U.S. dollar index was last up 0.11%, at 94.60, by 10:00AM GMT.

4. Earnings and economics

Clothing retailer Express (EXPR) will post quarterly results ahead of the open.

Another group of retailers -- including Calvin Klein parent PVH (PVH), Williams-Sonoma (WSM) and Guess (GES) -- along with HP (HPQ) will report after the market closes.

As for economic reports, the U.S. National Association of Realtors will release fresh July data on existing homes sales at 10 a.m. ET.

The U.S. Energy Information Administration is reporting weekly crude oil inventory data at 10:30 a.m.

This report can have a big influence on the direction of oil prices if there's more or less inventory than expected. Currently, oil prices are slipping by about 1.5% to trade just below $47.50 per barrel.