40mm is quite a bit though, could be too much to handle. Most of the rain is coming at night, but 5-10mm in the afternoon will be rough but it can still be a great time. I was out this weekend in 50km winds with only 1-3mm of rain and it was unbearable at times but worth it in the end. Going by the forecast if you go in the morning you should be able to get alot of hours of good fishing in. If you are going to float roe bring both small and larger bags, ive been surprised with how clear the river I fish has been this year after quite a bit of rain.