Warm ups in the weather often cause insects and other wildlife such as skunks to break dormancy earlier than normal. There is much to be done if you are a wild thing and as they say "The early bird gets the worm". In nature it really is survival of the fittest, better nesting locations, breeding grounds, mates, food supply, all these things go to the fittest. Queens can be dethroned by a more dominate, aggressive queen if that location suits her needs and the nest building hasn't proceeded too far along. In early Spring queens (wasps/hornets) spend copious amounts of time searching for the ideal nesting location. Protected from predators, ample food supply for larva and adults is vital to survival of the colony and water make for the ideal nesting location. Queens will bound from dark spot to dark spot looking for access points into buildings. Water can be supplied by garden hoses that drip, bird baths, pools, or anything that is able to collect water or even dew. Food sources are other insects, protein even grease and nectar, that's why you see them hanging around your hummingbird feeders. Location, location, location. Realtors know it, so do the wild things.
If a location was a hot spot for wasps/hornets last year, your first step should be to address the food, water and shelter issues. Caulk holes and gaps around doors and windows, check soffits to make sure they fit correctly, look for cracks in mortar between blocks and gaps under siding. Gaps in shingles or even in gutters that have gutter guard on them can prove to be handy nesting areas if the other needs are met. Mole tunnels offer a great in-ground home so make sure you address those issues as well by either tamping down the soil , rolling it or using a granular insecticide labeled for Japanese Beetles (moles eat the larva, get rid of the food source, get rid of the moles).
Clean up pest waste on a daily basis, wash garbage cans weekly and move those hummingbird feeders out farther from the house. Close the vents on your grill and cover it when not in use. Dump out standing water in sources such as children's sandbox toys, ashtrays and other items that are able to collect small amounts of water.
Pools and flower gardens, you're not going to remove them so you have to understand that they will act as a magnate for wasps/hornets. If there is a deck around the pool, this area should be treated on a regular basis during the season to prevent nests from occurring on the underside of the deck. Potted flowers are beautiful but refrain from placing them around the pool area.
Prevention is the key, it may not completely eliminate the chances of a run in, but it will tip the odds in your favor.