Continuing what's become a firmly established pattern over the past few weeks, cryptocurrencies slid sharply lower early in the U.S. trading day.

Ninety minutes after U.S. stock markets opened for trade following Monday's Labor Day Holiday, bitcoin {{BTC}} was down 1.5% to $57,800 while ether {{ETH}} was lower by 3% to $2,442, its weakest level since early February.

The broad market gauge CoinDesk 20 Index was down only 1% as a handful of constituents were posting modest session gains, led by lumens {{XLMX}} and litecoin {{LTC}}.

The selling in crypto took place alongside a sizable slide in stocks, led by a 2.4% decline in the Nasdaq and a 1.5% fall for the S&P 500.

U.S. August economic data begins to roll in

This morning's ISM Manufacturing PMI report for August showed continued contraction, coming in at 47.2 versus 47.5 expected and July's 46.8. The guts of the report, however, had a stagflationish feel, with New Orders dipping to 44.6 from July's 47.4 while Prices Paid rose to 54.0 from 52.9.

Following the soft numbers, traders have upped the odds of a 50 basis point Federal Reserve rate cut in September to 39% from 30% one day ago, according to CME FedWatch . The betting favorite, though, remains 25 basis points at 61%.

The main event for U.S. macro news – and possibly the final arbiter on whether the Fed goes 25 or 50 – remains Friday's August employment report, and economists are forecasting job gains rebounding to 160,000 from July's soft 114,000 print. The unemployment rate is anticipated to have dipped to 4.2% from 4.3%.

Seasonality suggests selling might continue

After bitcoin's roughly 10% decline for the month of August, at least some were hoping for a September bounce, but that could prove wishful thinking. According to Galaxy Research chief Alex Thorn , bitcoin fell during seven of the last 10 Septembers. However, that data set contains some good news, said Thorn, as October has typically been bitcoin's best month of the year and the rest of the Fall has usually brought positive returns as well.