Dutch police used some unique investigative skills to discover and shut down a drug house in Haarlem, Netherlands, in February of 2015, according to The Telegraph.

One officer's keen eye noticed a suspicious patch of roof that had no snow despite other snow-covered roofs surrounding it, which led the cops to a large-scale marijuana operation, according to The Telegraph. 
Cannabis, like most other plants, requires a specific environment to grow well. Maintaining the right heat and moisture levels allows growers to produce better plants. According to The Weed Blog, seedlings grow better in temperatures between 68 and 77 degrees Fahrenheit, but bigger plants may grow well in temperatures up to 82 degrees Fahrenheit. 

While the Netherlands permits personal use of marijuana and even allows some growing, individuals are only allowed to have up to five plants and may only carry up to 5 grams of weed. The home searched had an "industrial" size operation, which is likely what contributed to snowmelt, according to The Telegraph. 

Police officers all over the world have used different heat-seeking methods to discover grow houses although the heat signature is not 100 percent accurate. In 2011, British police officers raided a home they believed held a room full of marijuana plants based on a helicopter-mounted infrared camera reading. Unfortunately the heat signature was a space heater keeping two guinea pigs warm, according to Gizmodo.

Police took to Twitter to warn neighbors, "Look at the roofs in your neighborhood. No snow? It could be cannabis." Neighbors were encouraged to report suspicious homes to the police.