Should I do my dream Japan farm volunteering trip in July-August, or wait until April? First solo travel dilemma.

Hey everyone,
I need some advice because my brain is doing somersaults over this.
I’m a teacher in the UK and I’ve got six weeks off this summer. I’ve always dreamed of going to Japan, and I recently found a volunteering opportunity at a farm/guesthouse in Yamanashi — up in the hills with a view of Mt Fuji. It honestly feels like a once‑in‑a‑lifetime thing. The hosts seem lovely, other volunteers said it was unforgettable, and the work is light (lawn mowing, helping around the guesthouse, picking peaches). Plus, it would fall on my birthday week, which makes it feel even more special.
Here’s the problem:
I keep hearing how brutal the heat and humidity are in July–August, and as a British person who melts at 25°C, I’m scared I’ll be miserable. It’s my first solo trip too, so I’m already nervous.
I’d only be volunteering for a week, and it’s in the countryside rather than a big city, so maybe it’s more bearable? But I’m worried I’ll be uncomfortable the whole time.
My other option is to push it to next April, when the weather is way more comfortable and Fuji still has its snow cap. But that means waiting almost a year, missing the birthday timing, and possibly missing out on the exact vibe/people that are there this summer. I know I’d get FOMO sitting at home knowing I could have been in Japan doing something future‑me would be proud of.
So I’m torn between:
July–August:
Hot and humid

But it’s my birthday

I finally do the dream

First solo trip challenge

Summer farm vibes, peaches, long evenings

I don’t have to wait a whole year

April:
Perfect weather

Fuji with snow

Cherry blossoms

But I have to wait until next year

Different volunteers/hosts vibe

If you’ve been to Yamanashi in summer, or done farm volunteering in Japan, or just have general solo travel wisdom — I’d love to hear your thoughts.
Would you go in July–August for the experience, or wait for April for comfort?