ABC News’ analysis of COVID-19 trends in all 50 U.S. states plus Washington, DC and Puerto Rico found that there have been increases in newly confirmed cases over the past two weeks in 33 states plus Puerto Rico.

The average of new cases in the United States for seven days is now its highest level since Aug.22, a worrying national trend as health experts warn that cold temperatures will only exacerbate the spread of the virus.

The analysis also found increases in the daily positivity rate for COVID-19 tests in 25 states, an increase in hospitalizations for COVID-19 in 35 states plus Washington, D.C., and an increase in the number of daily COVID-19 deaths in 18 states.

Four states – Nebraska, Montana, South Dakota and Wisconsin – have recorded records of current hospital admissions for COVID-19 in one day. Nine states – all of them in the Midwest and West – have reported a record high of COVID-19 cases over the past seven days.

Since September 13, the national rate of new cases for seven days has increased by about 25%.

All trends were analyzed from data collected and published by the COVID Tracking Project over the past two weeks, using the linear regression trendline of the seven-day moving average.

ABC News’ Benjamin Bell, Brian Hartman, Suren Kim, and Ariel Metropoulos contributed to this report.