The summit will hear that summer rainfall may drop by more than half in the south and east of the country, causing acute water shortages and seriously damaging farms.
The summit - which will bring environment ministers Elliot Morley and Lord Whitty together with top officials from the National Farmers Union, the Tenants Farmers Association and the Country Land and Business Association - will also hear that farmland may have to be abandoned to increased winter farming.
But, in compensation, a hotter Britain is likely to be able to grow more of its own wine.
The papers say that scorching summers will become increasingly frequent with global warming, with "very hot Augusts" - such as in 1995 - happening once every five years by 2050. Less rain will fall, and more moisture will evaporate from the soil, causing droughts.
They say: "Hotter and drier summers are likely to result in a seasonal reduction in available water resources and the increased risk of drought. The areas currently under most pressure from agriculture will become further stressed as the regional effects of change are felt."
In winter, Britain will face the opposite problem, as rainfall sharply increases.
Rivers will flood so much more frequently that the Government will no longer "be able to justify maintaining current standards of protection". Winter crops will also suffer as most of them need cold to "vernalise" them.
By contrast, farmers could reap some short-term benefits from global warming as the growing season increases and higher levels of carbon dioxide in the air encourage crops. The papers expect that farmers will also benefit as global warming hits competing countries harder.
Special report, pages 10-11