Around 29,000 pubs will be unable to reopen if coronavirus restrictions are relaxed to allow outdoor service in April, according to the British Beer & Pub Association (BBPA).
The trade body said the majority of venues do not have a big enough garden or outdoor space to accommodate customers.
Emma McClarkin, chief executive of the BBPA, said the risk of rain disrupting trade means a partial reopening is not "commercially viable".
The BBPA is calling for pubs to reopen for both indoor and outdoor customers at the same time as non-essential retail.
It said around 75% of UK pubs have a beer garden or outdoor space, but only 40% have a large enough outdoor space.
This means just 17% of pub capacity would be able to open, resulting in a loss of turnover to the sector of £1.5b compared to normal trading.
McClarkin said: "Even if some pubs did try and open outdoors only in April, all it would take is some heavy rain and they would find it has all been for nothing.
"For many pubs, gardens are at the back and the only way to access them is through the inside. And of course, toilet facilities would still need to be provided.
"We question the government's thinking behind this and suggest they consult with us as a sector on it."
Pub sector chief executives have pulled out of government talks with business minister Paul Scully over what Young's boss Patrick Dardis described as an "obvious lack of interest and respect".
In a latter to the prime minister, Dardis accused ministers of "playing politics" and said they had not engaged with the sector in a "meaningful way".
The BBPA published its roadmap to recovery last week, calling on the government to extend support for pubs to prevent thousands of closures.