NEW YORK - Wall Street investors were rattled Monday as stocks took a dive following declines in China.

The Dow closed down more than 276 points -- its biggest loss in two weeks.

Jesse Mackey, chief investment officer at 4Tought Financial Group, says people should be looking at their portfolios and talking with their advisers.

Mackey says the month of January as a whole can be telling.

"The 'January Effect' has historically given at least some indication of the future direction of the markets for the remainder of the year," he says.

Part of the trigger behind all the selling on Wall Street Monday was a huge plunge in China's market due to low manufacturing numbers. Rising tensions between Saudi Arabia, a huge oil supplier, and Iran are another major factor.