A key signal suggests job growth could plummet in coming months amid labor strikes and bad weather

• A key signal suggests monthly job growth could plummet in the coming months, according to Ned Davis Research.
• The research firm highlighted that a slow-down in temporary hiring services is the canary in the coal mine.
• "Seasonal adjustments, weather, revisions, and strikes are all likely to impact the trend," NDR said.

The solid job growth seen in the labor market over the past three years could be coming to an end in the coming months, according to a Friday note from Ned Davis Research.

The investment research firm highlighted a key leading indicator that is warning of a potential slowdown in hiring, and that's the hiring activities of temporary hiring services.

"The industry losing the most jobs has been temporary help services. That hasn't been a good sign historically," NDR's chief global macro strategist Joseph Kalish said.

The recent slowdown in temporary help services comes amid ongoing labor strikes, bad weather, and the likelihood of lower revisions to the monthly job numbers.

"Although job growth is clearly slowing, there are reasons to believe the July numbers were overstated, underlying growth is weaker, and is likely to slow even further in the months ahead," Kalish said. "Seasonal adjustments, weather, revisions, and strikes are all likely to impact the trend."

While warm weather often helps boost seasonal employment, this summer's extreme heat could have the opposite effect as outdoor venues likely suffered from fewer patrons, according to Kalish.

Signs of a slowdown in job growth has been apparent over the past two months, as the three-month average of non-farm payroll additions has fallen by 10,000 each of the last two months. And the two most recent job reports also came in below economist estimates, ending a more than year-long streak of better-than-expected job growth.

Other factors that could limit future job growth includes tighter lending standards and a potential strike by the UAW and other unions.

Finally, the decline in the average workweek is another leading indicator that has been moving lower more recently. That's not a good sign for employer's future hiring ambitions.

"Employers prefer to reduce hours rather than cut headcount. But at some point further workweek reductions become impractical and layoffs pick up," Kalish said. "Companies stop hiring before they start firing."

With many stock market bulls pointing to the strong labor market and resilient economy as good reason to stay long stocks, that could change quickly if the job market really does turn south.