Chief Executive Hugh Morris says "focus for the season will be on hosting all matches at our main venue, Sophia Gardens."
The ECB and the 18 first-class counties are still working together to develop a fixture list that balances the demands of domestic and international cricket alongside the demands of public health and safety.
Mr Morris, said, “We were looking forward to our annual fixtures in Swansea and Colwyn Bay, and taking one-day cricket to Newport for our 2020 season.
"It is with regret that we today announce that the logistical challenges of hosting outground cricket simply cannot be met in this current, uncertain climate.
“The domestic fixture schedule for 2020 has yet to be determined, but if cricket is able to safely return, our focus for the season will be on hosting all matches at our main venue, Sophia Gardens.
"We remain committed to taking Glamorgan games across Wales for wider communities to enjoy, when we are able to do so safely and securely.”