Growing in rainy-summer climates. What’s it like?

Some people live in some seemingly mythical places where summer and rainfall always go together. That must produce some unimaginably productive greenery! Sure weeds would be a constant problem, but I’d take that problem over dry waterless soil that kills plants by thirst. It doesn't matter how good your soil is or how well it's mulched: most plants and trees will die without water. That's my main problem half the year.

Are the tropics the only places in the world where people get generous rain during summer? I get lots of rain in winter only and boy does my land go from light brown to completely green in just a few weeks. I can only imagine what it would be like with warm weather.

Yep, I get rain all summer. Loads of it. About 80 cm in four months.

Then I get eight months without a drop off rain...

I get rain all summer infact July and August are the wettest months, but not by much rainfall here is pretty evenly spread. We don't need to irrigate, I and my parent in law grow vegetables commercially without irrigation, without mulch (just a slug house that keeps the soil cold) And without any water retaining earthworks, infact we spend a lot of money on drains, mole-ploughs, ditches and in general getting RID of water as fast as possible!
Of course it is not as warm here and it is very humid, 80-90% is normal (right now it's 83% and 8C with bright sun and very little wind)

Fear the temp and precip charts for my area!

https://weather-and-climate.com/average-monthly-Rainfall-Temperature-Sunshine,Hamburg,Germany

Winter precipitation is drizzle and/or snow in the winter, and hard fast thunderstorms in the summer.  It took me forever to understand this, coming from the PNW and increasingly harsh summer droughts.  

It's nice that I don't worry about watering things except:  When planting, still new and fragile, in pots, and/or an actual dry spell.  I was way too cocky last year, and after a dry spell of almost a month with deeply unpleasantly hot temps, my potted mint died.  I've never killed mint before* - I'm so proud!

For fragile plants, I suppose I should shelter them in some way from the hard summer rain, but I'm not that sophisticated yet.

*Except Corsican mint, which dies if you look at it.  I am bitter at all the pots I bought guaranteeing to be a "step-able" groundcover in the PNW, yet I still bought some this year for some experimental decorative plantings in Hamburg, hoping the different weather will work.  They are currently languishing at the point of death on my windowsill.  Argh.

Our rainfall pattern in this part of NZ seems to be shifting to a more Mediterranean mode with drier summers, but it's really easy to tip with one or two decaying cyclones wandering our way. Some summers are pretty droughty, like the one we just had...only enough coming every 3-4 weeks to keep the grass from completely going brown. Other years we get nice, evenly spaced dumps thanks to tropical-origin atmospheric rivers, and can average 10 cm a month right through summer. Then there was the Schizo Summer of 2017-18, which started off extremely hot and dry and then flipped around the end of December into an almost monsoonal wet mode with three ex-cyclones in succession (along with their attendant wind damage, floods and coastal erosion).

I won't take anything for granted here and storing water in and out of the ground has always been an obsession of mine. The wet summers are easier with less need to water, but the other side of the coin is weeds and fungal issues like blight. Dry summers mean that I spend lots more time watering and keeping an eye on the nut trees, which are the first to complain. Fruit, OTOH, was brilliant this year.

Here in southern (non-tropical) Brazil it`s changing. We used to have predictable short summer thunderstorms nearly every afternoon. But last summer we went more than 35 days without rain during the height of summer, and so I ended up doing two "seasons" of summer plantings, Pre-Scorch and Post-Scorch. We've had unseasonable cold snaps and hot stretches, it's getting much less predictable.
As a result, I put in a few more rain barrels and am also now thinking much more seriously about capturing rainwater.