Unlike extended droughts which can last for years on end, summer droughts are seasonal droughts which can return year after year, and which are usually broken by a standard seasonal change in the local weather patterns. Different parts of the world have different expectations about rainfall: so there can be no single definition for when low rainfall officially turns to drought. For practical purposes, however, a dry spell becomes a drought when the amount of rainfall during the dry season is both significantly less than normal and falls significantly short of normal local needs.
Summer drought can easily damage established agricultural patterns and destroy entire crops. All it takes is a few steady weeks without rain during a critical period in crop germination or growth.
The truly devastating summer droughts are the ones which come unexpectedly: especially after a winter with low snowmelt. Even a few weeks of this kind of summer drought can wipe away an entire agricultural year. When such a summer drought hits an area whose water supply is already stressed from previous low-precipitation years, even irrigation may no longer be an option. Very few crops can survive on almost no rain at all.
A summer drought deep enough to destroy crops will also devastate farmers and all the employees which depend directly on the farming sector for their livelihood. With no crop, farmers have no reason to hire seasonal workers. With no crop income, farmers may not be able to meet debt deadlines. The boomerang effect on the economy may be very far-reaching.
No biosphere on earth can survive for long without water. Wetland environments may be destroyed completely. Every ecological niche is vulnerable, from the smallest insect on up. A wetland species may recover from an occasional summer drought, but a severe one could make the difference between survival and extinction.
A deep summer drought stresses even established trees, making them more vulnerable to insects and disease. Diseased and dead trees catch fire easily.
Lightning storms don't go away just because the rain has. A lightning strike in tinder-dry forests will set them ablaze in no time. Even parts of the waterlogged Everglades have dried up enough to catch fire. Even normal activities can create the spark which sets everything ablaze. A hot automobile exhaust pipe can set fire to nearby grass. Fast-moving trains shed sparks from their wheels.
A drought which has killed off the local vegetation also kills off its root system. Nothing remains to hold the topsoil in place. If the drought still does not break, that valuable topsoil blows away in the wind. Where the air is dry enough and the wind is strong enough, it can create a dust storm.
City folk and tourists frequently see droughts - in the absence of vicious heat waves - as a sunny vacation without rain and thus something to celebrate: but even for tourism, droughts can be a mixed blessing. Tourists to the Greek isles celebrate its almost perfectly sunny summertime weather on the beaches: yet both tourists and locals in Athens and other large cities may curse the lung-choking "nefos" that comes alongside the summer drought to rot away historic marble architecture. The classical Greeks who built the Parthenon never envisioned the modern smog caused by summer atmospheric inversions.
Sometimes the breaking of the drought can be as devastating as the drought itself. Indian summer droughts are typically broken by the arrival of the monsoon season: and that rain is very, very welcome after weeks and months of blazing hot temperatures which are among the hottest on the face of the earth. In 2010, however, an extended brutal heat wave was broken by a devastating monsoon season which flooded a third of Pakistan, completely disrupting the growing season and ensuring hunger in the year to come.
With any summer drought, food prices and water prices are certain to rise, possibly beyond what people can afford to pay. The market cares not at all. Scarcity drives price upward. If price happens to go beyond what people can pay, they will sicken and starve. If they can, they will migrate: in turn placing water-stress on new regions.
A series of summer droughts can become a permanent state of drought, especially once existing water resources are depleted beyond the ability to replenish. Technically, it is no longer drought once the region becomes desert.