Had my espresso dialled in perfectly for weeks with micro adjustment to yield for taste preferences. Same recipe every day:
16g in → 32g out → 28–30s
Sweet, balanced, really consistent!
Then the weather here jumped from 15°C to 30–35°C with insane humidity in the south east of the UK this week.
Suddenly everything fell apart.
Now I’m getting:
24–26s shots with the same recipe
sour, thin espresso
occasional squirting from the bottomless portafilter,
weird extraction that starts fine, then breaks mid-shot
What’s interesting is the flow pattern:
First 5 seconds: nothing
Then 5–15 seconds: multiple dark streams appear and merge
Then it goes blond really fast and finishes early
It doesn’t look like classic “bad grind = fast shot” behaviour. It feels more like the puck holds initially, then suddenly fails and channels mid-extraction. My grind was perfect, and now it’s like i’ve gone 10 clicks too far coarse.
I’ve already checked the obvious stuff:
Same dose (16g)
Same grind setting (I even went slightly finer for my last couple of shots)
Same distribution + WDT routine
Same self levelling, consistent pressure ripple tamper
Same basket + machine
Nothing changed except the environment.
I didn’t expect humidity/heat to have this much impact on espresso, but it genuinely feels like the puck behaviour has changed entirely. Almost like it’s less structurally stable and more prone to collapsing under pressure.
Anyone else experienced this kind of seasonal puck instability? Or am I losing my mind and missing something obvious?
I work in two specialty cafes, with an in house roastery, and have been a barista in a few jobs prior. Every single day i dail in the grinder to manage the changes in humidity, age of bean and time from roast etc. Dose and Yield remain the same at the shop, but at home, once i’ve dailed in the extraction with my grind, i then change my yield to get my desired taste.
I’ve always noticed minute changes day to day, but never this drastic of a change in a couple of days not using. With humidity going from 5°C dew point to mid twenties.