The stock market has had a horrific 2022, and investors have hoped that they'd get some relief in the last week of the year. Tuesday morning brought the promise of at least a mild bounce for the financial markets, as stock index futures were modestly higher before the market open.

Many market participants pointed to news from China as a reason for the gains, as the Chinese government announced that it would lift many pandemic-related restrictions on incoming international travelers in early January. Yet shares of electric vehicle (EV) stocks Tesla (TSLA -2.83%) and Nio (NIO -1.14%) continued to move lower in premarket trading on Tuesday morning, and questions about the sustainability of demand for EVs in China and elsewhere around the world are a big part of why the two EV stocks have been stuck in a big downtrend lately.

Is Tesla cutting Chinese production?

Shares of Tesla fell about 5% in premarket trading early Tuesday. The pioneering EV manufacturer was the subject of multiple reports that it has made changes to its current and future production plans at its Gigafactory in Shanghai.

Tesla extended a planned eight-day production halt in Shanghai, according to The Wall Street Journal. The report cited a massive wave of infections from COVID-19 in China that are having an impact on Tesla's Chinese workforce and the manufacturing capacity of its suppliers.

Another report suggested that Tesla might keep manufacturing well below capacity throughout January. Reuters cited internal Tesla schedules in concluding that the automaker will start operations back up on Jan. 3, but then halt production from Jan. 20 through the end of the month. The move lines up with the Chinese New Year holiday, but as Reuters noted, Tesla doesn't have a history of suspending manufacturing operations at this time of year.

Regardless of what actually happens, Tesla investors are concerned about the potential for demand for the company's EVs to fall off in a key market. The company might not confirm any impact on total production until it releases first-quarter 2023 figures in early April, but reports like these should shed some light on what actually happens sooner than that.

Nio expects weaker deliveries

Investors got more transparency from Nio, whose shares dropped 5% in premarket trading Tuesday morning. The Chinese EV manufacturer revealed in a press release that its delivery volume in the fourth quarter of 2022 wouldn't be as high as it had previously anticipated.

Nio said that it now expects to deliver between 38,500 and 39,500 vehicles for the period from October to December. That's down from the 43,000 to 48,000 range that it had adopted earlier for guidance.

In explaining the shortfall, Nio said that the outbreak of COVID-19 hitting major cities throughout China has created a wide range of business challenges. The problems have affected both production and delivery of Nio vehicles, and they are exacerbating supply chain constraints that were present even before the latest outbreak. Despite the company's best efforts to sustain continuous operations, Nio has been unable to keep working at full capacity.

Nio tried to be upbeat about its future, pointing to the 2022 Nio Day event on Dec. 24 at which it launched its EC7 and ES8 smart electric SUVs. Yet as with Tesla, Nio will rely on ongoing consumer demand to determine whether it will prove successful in its efforts to stake a claim in what has been until now a fast-growing EV market in China.