Summer is the season in which the game typically begins, and is longer than its counterpart, Winter. By default, in Sandbox Mode summer lasts for 20 Days and resumes after 16 days of Winter. Adventure Mode worlds have different seasonal variations.
During Summer, most creatures are active, and the days are longer. Crops grow, and Food is easier to find. Rain occasionally falls during Summer, which reduces Sanity and may result in Lightning strikes; however, it also speeds up crop growth. Food spoils 25% faster during summer.
The Mactusk N' Son hunting party is not present at their Walrus Camp during Summer. Red Hounds may occasionally appear rather than Blue Hounds during periodical Hound attacks. Redbirds and Crows appear and the Koalefant appears with a reddish hide.
During Summer, the world is presented in a sepia tone as opposed to the blue tint in winter.
In the Reign of Giants DLC, Summer is replaced by Autumn and is given its own season along with Spring. It lasts for 16 days by default. Therefore, the first Summer will last from day 21 to 36, or from day 56 to 71. Summer leads into Autumn. Summer is indicated by the world having a more sepia-toned tint than normal, which changes in brightness periodically, and by DSP which causes sound effects and music to sound far away and hot, similar to Winter's muffled sounds. Days are also much longer in Summer, with Dusk being the shortest, lasting just one segment during mid-season. The length of the Night is average.
During Summer, plants will wilt and require fertilization in order to regrow, and food will spoil 25% faster. Plants return to normal a few days into Autumn, even without fertilizer. On the other hand, fertilized crops tend to grow fast due to longer daylight but not as fast as during spring due to less rain.
Due to longer days, daylight-related Sanity is less of an issue than in other seasons.
Occasionally, the Dragonfly can be encountered. It will roam around the landscape, setting nearby structures on fire.
Main article: Overheating
The intense heat provides the challenge of the season. Similarly to freezing in the Winter, an unprotected player will suffer damage from Overheating. The player can use or wear items such as Ice, an Ice Cube or a Chilled Amulet and can stand under a tree to cool themselves. They can also use the shade from a Straw Hat, Umbrella or Eyebrella, or wear a Summer Frest or Floral Shirt to delay the rate at which they overheat. The player can also freeze a Thermal Stone (or two) in an Ice Box or Snow Chester or stand near the Endothermic Fire to cool it and themselves.
Additionally, the Summer season experiences a drought, and items can ignite and burst into flames. When the world temperature is above 80 Celsius degrees, every 45 seconds, the game attempts to set a burnable object within 25 units, or 6¼ pitchfork tiles, of the player (or near every player, excluding the ones in the Sandstorm ) on fire. There is a 20% chance that this attempt will succeed. This includes plants, such as Berry Bushes, mobs, and even structures like the Science Machine. Caution is advised as the fire will keep spreading. When Structures have been burnt down, players can hammer them down to recover half the components, including single components. Wildfires occur only on the surface and only when it is not night or dusk time.
Items and Structures can be protected from combustion by using an Ice Flingomatic, which will fire snowballs at flaming objects. Objects will only combust when near the player, so they may also be protected simply by avoiding them until Autumn.
An object nearing its combustible point will begin to smolder first and visually smoke. The player's character will comment on it when it is examined. Smoldering objects can be manually cooled with Ice, Fertilizers, an Ice Staff or with the player's hands (causing damage of 5 for the player). The eventual fire created by a smoldering object will cause other flammable things near its vicinity to near-instantly burst into flames as well, quickly spreading the fire.
In Don't Starve Together, any fires will first make nearby flammable objects smolder as well, meaning wildfires don't spread as fast as they do in the single player game. Wildfires also will not occur within a Sandstorm, which makes Antlion's Desert an optimal area to build a base.