400 would work if temps peaked at 23-24max June July with one proviso... 200 mm needs to fall april, may and june.
400 is a bloody disaster if 50 or less falls may june.
Sodden winter followed by dry or very dry early summer is the single worst scenario.
Dry winter followed by cool and wet ( by our standards ) early summer is "grain shed isn't big enough"
300-350 mm being enough here is a laughable idea ( otherwise you would cry).
91/92 growing season iirc, maybe 92/93 was 12.5 rain-guage inches for the growing year, and it wasn't funny.
Maintaining grass quality during mid-season grazing is important. Farmers can maintain quality by entering ideal grazing covers of 1,300 – 1,500kg DM/ha, and grazing down to a residual of 4cm every rotation.
If you are now in a situation where cows are not cleaning out paddocks as well as they should be, leading to the development of steamy grass within the sward, here are some options.
Common options for rejuvenating swards include:
Take a silage cut, probably into bales, remove the material and start again with the aftermath...