Nighttime temp and humidity unstable

If the temperature is not stable your heater is too small, your lung room is too unstable. One option would be insulating of your box, but could screw you up when the lights turn on ;-). Another option (if your lung room is dry) would be more inlet. Nonetheless, I would try it without the heater and compare. As you can see in your measurement, your RH and temperature are directly linked. So your humidity is most likely caused by temperature. It seems like your heater needs to long to heat up your lung room. So put it in there and turn it on before the lights turn out.. or something else. If your temperature does not drop too low without heater and you got no mold problem ; I would turn it off. Just as reminder the positioning of your sensor and airflow in your box are also crucial.

🌙 Looking at your current data: Night temp range: ~68.5°F to 76.2°F Humidity: fluctuating between ~46% and ~69% VPD: fluctuating (min 0.90, max 1.70 kPa) ✅ What’s good: Your temperature doesn’t drop dangerously low (you’re staying above 68°F). VPD (0.82 kPa average) is acceptable for late veg or early flower. The fluctuations aren’t catastrophic, but the spikes might be stressing the plant if too frequent. 🧠 Recommendations: 1. Let it cool slightly at night (if natural) Cannabis expects a temperature drop at night (a 5–10°F drop is totally normal). A bit of cooling stimulates stronger metabolism and resin production. So: if the temp stays above 64–65°F, you can skip the heater — no problem. 2. If you still want to use a heater: Use one of these control methods: ✅ Thermostatic plug (heater turns off when set temp is reached) ✅ Smart plug + temp probe (e.g. with Inkbird or Govee Wi-Fi controller) ❌ No direct plug heater running full blast – that’s likely what causes the spikes. 💡 Ideal night temp: 66–72°F 💡 Ideal night humidity: 50–60% 💡 VPD target (night): ~0.8–1.2 kPa 🔧 Bonus tips: If humidity climbs too high at night (70%), consider a small dehumidifier or better air exchange. Strong fluctuations in humidity + heat can lead to powdery mildew or botrytis in flower — especially when buds are dense. Summary: 🔥 Heater ✅ Only if temp drops

a question about stomata for 00110001001001111O u're saying that stomata is closed at night so that's mean that traspiration are slowing right what means humidity also slowing right ? so why then after 12h of dark i got humidity upto 70% when at light hours it's only get upto 50%(also using Co2 these hours)?

Great thing about the lights being off is the stomata are closed up tightly, for the most part. You should avoid lower temperatures if you can. You go much below 18c and you fuck with biological processes. Depending on how much money you want to spend you may find avoiding extremes is 'enough.' Or, if you want to spend a bit more, reduce the difference between night and day further. This is reference info you can google for a more precise answer. I think to avoid 'extremes' you want less than a 10F difference? i'm not googling it, but you can find that type of reference info easily enough on your own as far as what to target if you want to tightly manage it. Your RH spiked because temps dropped. If it showed absolute humidity, it would be a fairly flat line because transpiration is minimal at night - again, stomatas are mostly closed during this time frame and the steady absolute humidity is proof of that. The changing temperatures are the vast majority of the cause of RH oscillating in this particular graph. What is causing a 10F drop at 1am? It looks like every hour your temp just drops 10F. That's a large range if caused by a space heater. At least around here, those mostly are a 4-5F range... temp drop 1F below, turns on until it reaches +3F being the standard for the lasko brand and shuts off. Should see a ~4F range oscillation result. So, is this the equipment or is something cyclically happening in your house that you might be able to avoid its influence on the grow area -- like closing a door at night etc. if it is the equipment, there's not much you can do about the resulting range of temperatures. In the end, i wouldn't throw too many resources at this. Avoid mid 60F and below at the least. If you don't mid teh extra expense, keep it closer to 20c or within whatever range you found while googling reference material. If 'they' say staying within 5F of daytime temps is optimal, do that etc.. If i recall it's better if vpd doesn't swing wildly either, but again with stomata closed it's less of an issue during lights-out cycle. Again, more reference info you should look up and not rely on user-submission. Go find a reputable source for the exact details... and a vpd table to help choose what RH to target relative to targe temperatures at night.

Photosynthesis by day. Cellular respiration by night. VPD primarily affects transpiration rate, not cellular respiration. Cellular respiration, which releases energy from glucose, is primarily affected by factors like temperature and oxygen availability, not VPD. Should not be running 70+ rh overnight for any reason indoors, respiration will be crippled, stomata will shrink without the latent heat to assist, evaporation will cease. At 80rh stomata will close entirely preveting 100% of gas exchange, which will cease respiration and root respiration. Plant will spend entire night and process 0 carbon and be left with 100% stored in the stem. 0 atp for active nutrient uptake, 0 energy for anything. Vpd for daytime not for nights. If you don't control that rh with a negative pressure over night the lack of oxygen diffusion along, complete lack of atp production therfore plant will be severely limited in what it can do the next morning. Doesn't matter how much dli you give her, doesn't matter how much carbon she captures if it's not being processed from carbon into usable atp energy overnight, then the entire growth of the plant is limited to its energy supply. Anyway. Have fun whatever advice you choose. Wish you best of luck.

Ich würde die Beleuchtung nachts anschalten und dafür tagsüber aus. Dann sollte der Heizlüfter nicht nöt

O to add onto my thought, Its ok when temps flux between 10-12c at night from day time temps. IDK what this is in "freedom" units, but google should help yea figure that out. the scale is not linear so the further away from the center when c/f are the same (-40) the temps are more extreme in difference.

I would let it cool and just increase its ventilation to help reduce the RH. At night the RH can boost, its best to water your plants in the morning if you do it by hand to help avoid this. Hard to tell the scale on that graph, don't know if its grand fluctuations of like 10-15 degrees or if its small like 2-3. I still more airflow at night would solve it.

Hey 👋 In General it’s not a very huge problem if temperature and humidity rises & falls. Temperature shouldn’t fall lower than 15 C, as this slows down the metabolism of the plant. The humidity shouldn’t raise higher than 70% as otherwise your buds will get mold pretty fast. John_kramer already mentioned a very good solution. If you grow at night when the temperature falls and the humidity raises naturally, and let her rest within the day peak, you will automatically get lower ups and downs. Hope that helped 👊🍀🖖

Don‘t know which setting you Are using but I work with automations set by myself… I set the Temp stabel ( 21-22 C in Night ) und let regulate throug VPD set the Humidity ( humidifer )… it‘s normal that humidity rises After daytime, plants love a stabel temperature more than a stabel VPD/ Humidity

Just keep it under 70% hum and over 19C, and you will be fine. Reduce the Hum further in the later flower for obvious reasons down to 50-60% max.

that is what id expect to see, trend-wise... if you flipped when your lights were on, you'd 95%+ just see this same chart with the PM and AM swapped, because like your equipment is driving this/not driving it

u can change the hours grow at night and let it sleep by day