The majority of pharaoh ant invasions occur during winter rainstorms and summer droughts. These ants are most likely to enter homes in cold, wet conditions, a typical winter in Delta. A smaller peak in the level of infestation occurs during hot, dry conditions typically in August and September. Ants invade kitchens and dining rooms to escape heat or excessive dampness. They come in because of the weather, and they go out because of the weather. Pharaoh ants have many queens, and the workers can go back to any nest, so it’s impossible to kill off a colony by killing off one queen, most pesticides are designed to eliminate single-queen species. Using bug spray, bait and other household pesticides to prevent ant invasions are futile. A variety of retail ant killers I’ve heard of include: bleach, ammonia, soap, Windex, hot pepper, chili oil, lemon, vinegar, Raid, Black Flag, Hot Shot, Combat, Grant’s and Ortho Ant Kill. None of these products are effective in preventing ant invasions, although some will help reduce insect abundance following a rainstorm or during periods of drought.
https://www.linkedin.com/pulse/pharaoh-ant-invasions-determined-weather-randy-bilesky?published=t
http://www.delta-optimist.com/opinion/blogs/blog-pharaoh-ant-invasions-are-determined-by-weather-1.2372042