How to Store Weed and Keep It Fresh
Flower changes once it is packaged. A year-long laboratory study gives the clearest numbers we found on how. This page keeps what the study found apart from our own advice, and says what the study did not cover.
What the study tested
The authors are affiliated with the Technion Israel Institute of Technology in Haifa, Israel(flower storage study).
The team stored cannabis flower in the dark at various temperatures (25, 4, −30 and −80°C) and analyzed the profiles over the course of 1 year(flower storage study).
It worked with two varieties, a THC-rich one and a CBD-rich one. Aroma compounds, the terpenoids, were measured in the CBD-rich one only, at the start and at four months.
What it found
Storage at 25°C led to the largest changes in the concentrations of the natural phytocannabinoids over time(flower storage study).
The Δ9-THCA concentrations for the Type I whole and ground samples decreased by approximately 33% following 1 year of storage at 25°C(flower storage study).
The average terpenoid concentration decreased by more than 50% at t4(flower storage study).
Terpenoid concentrations were found to decrease rapidly under all storage conditions, but the lowest temperatures and grinding of the inflorescences were the least favorable conditions(flower storage study).
Storage of whole inflorescences at 4°C was among the optimal postharvest conditions for Cannabis(flower storage study).
What the study did not test
The study did not test a home freezer, a home refrigerator, humidity packs, container types or finished pre-rolls. Its aroma result comes from one CBD-rich variety, and every sample was held in the dark, so it says nothing about light. It measured chemistry, not how flower smells or smokes to a person.
A setup, with our view labeled
- Keep flower in the sealed, opaque package it came in.
- Our view: store it somewhere cool and dark, such as a closet or a drawer away from a stove, radiator or window. The study supports cool over warm.
- Our view: keep it whole and grind only what you plan to use, which fits the finding about grinding.
- Our view: keep it out of the car, off the sill and away from the dryer.
- If you move flower into a jar with a tight lid, keep the jar out of light too.
Humidity
Before storage, the flower was cured for 1 month in the dark at 21°C and 60% humidity(flower storage study).
After curing, both varieties contained 9 ± 0.3 % w/w moisture(flower storage study).
The study did not test other humidity levels, and we found no Massachusetts rule that sets a home humidity target, so a number on a humidity pack is the pack maker's, not the state's. If flower is damp, do not seal it in a container.
Children and the law
If you have more than two ounces of cannabis in your home, it must be locked in a secure place(CCC Know the Laws).
The Massachusetts weed laws page has the rest of the home rules. For mold, see how to tell if weed is stale or bad.
Short answers
What is the best way to store weed?
Keep it in a sealed, opaque container, whole, in a cool, dark place. In the study, whole flower at 4°C was among the optimal conditions, and 25°C changed cannabinoids the most(flower storage study).
Should I store weed in the freezer?
The study found the lowest temperatures were among the least favorable for terpenoids in the one variety it measured. It did not test a household freezer, so we make no claim either way.
Do humidity packs work?
The study did not test humidity packs, and we found no Massachusetts home target. Treat any number on a pack as the maker's claim.
Keep reading
- How to Tell If Weed Is Stale or Bad
- How to Store Pre-Rolls
- How Long Do Pre-Rolls Last?
- Massachusetts Weed Laws: What Is Legal
- COA library: the lab report for each AC strain
- All AC guides
Sources
- Milay et al., “Metabolic Profiling of Cannabis Secondary Metabolites for Evaluation of Optimal Postharvest Storage Conditions,” Frontiers in Plant Science 11 (2020) (read November 5, 2026): "Technion-Israel Institute of Technology, Haifa, Israel"
- Milay et al., “Metabolic Profiling of Cannabis Secondary Metabolites for Evaluation of Optimal Postharvest Storage Conditions,” Frontiers in Plant Science 11 (2020) (read November 5, 2026): "stored in the dark at various temperatures (25, 4, −30 and −80°C), and their phytocannabinoid and terpenoid profiles were analyzed over the course of 1 year"
- Milay et al., “Metabolic Profiling of Cannabis Secondary Metabolites for Evaluation of Optimal Postharvest Storage Conditions,” Frontiers in Plant Science 11 (2020) (read November 5, 2026): "a storage temperature of 25°C led to the largest changes in the concentrations of the natural phytocannabinoids over time, making this the most unfavorable temperature compared with all others examined here"
- Milay et al., “Metabolic Profiling of Cannabis Secondary Metabolites for Evaluation of Optimal Postharvest Storage Conditions,” Frontiers in Plant Science 11 (2020) (read November 5, 2026): "the Δ9-THCA concentrations for the Type I whole and ground samples, decreased by approximately 33 % following 1 year of storage at 25°C"
- Milay et al., “Metabolic Profiling of Cannabis Secondary Metabolites for Evaluation of Optimal Postharvest Storage Conditions,” Frontiers in Plant Science 11 (2020) (read November 5, 2026): "the average terpenoid concentration decreased by more than 50% at t4"
- Milay et al., “Metabolic Profiling of Cannabis Secondary Metabolites for Evaluation of Optimal Postharvest Storage Conditions,” Frontiers in Plant Science 11 (2020) (read November 5, 2026): "Terpenoid concentrations were found to decrease rapidly under all storage conditions, but temperatures lower than −20°C and grinding of the inflorescences were the least favorable conditions."
- Milay et al., “Metabolic Profiling of Cannabis Secondary Metabolites for Evaluation of Optimal Postharvest Storage Conditions,” Frontiers in Plant Science 11 (2020) (read November 5, 2026): "storage of whole inflorescences and extracts dissolved in olive oil, at 4°C, were the optimal postharvest conditions for Cannabis"
- Milay et al., “Metabolic Profiling of Cannabis Secondary Metabolites for Evaluation of Optimal Postharvest Storage Conditions,” Frontiers in Plant Science 11 (2020) (read November 5, 2026): "inflorescences were cured for 1 month in the dark at 21°C and 60% humidity"
- Milay et al., “Metabolic Profiling of Cannabis Secondary Metabolites for Evaluation of Optimal Postharvest Storage Conditions,” Frontiers in Plant Science 11 (2020) (read November 5, 2026): "both chemovars contained 9 ± 0.3 % w/w moisture"
- Cannabis Control Commission, Know the Laws (read November 5, 2026): "If you have more than two ounces of cannabis in your home, it must be locked in a secure place."