Trading depends on having a ready number of other traders prepared to buy and sell your proposed offers. During pre-market hours, because there are fewer traders, it can be more difficult to execute some of these trades. Some stocks might not trade at all. These factors can make it more difficult for you to execute a trade.

Because there is less trading volume and fewer traders, you may find it hard to align your bid price with an ask price during pre-market hours. That means you may struggle to get as favourable terms as you would during normal hours, making it more difficult for you to execute a trade.

Many online trading systems only accept limit orders during pre-market trading to protect traders from volatility. Limit orders are only executed at a specified price and ensure you don't buy for more or sell for less on your order. Because of volatility, an asset's price might move away from your limit price. This makes pre-market limit orders susceptible to not being executed.

Because of the limited number of trades and low volume, pre-market moves are by no means an indicator of a share price's movement during normal trading hours. An asset's price could reverse or stall when the markets open, which could leave a pre-market trader out of pocket. Volatility of a share price could also increase, particularly based on overnight news.

While you may get ahead of some of the competition through pre-market trading, you can still be faced with new competition that may be difficult to overcome. Pre-market trading also attracts bigger institutional investors, who may have access to more information than retail traders.

Because most pre-market trading is done online, it's prone to systematic computer delays that might affect the execution, cancellation or changing of your trades.