An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The season that starts when the Sun, during its apparent yearly motion, attains the celestial longitude 90 degrees in the Northern Hemisphere and 270 degrees in the Southern Hemisphere. The current length of the summer season, around the epoch 2000, is 93.65 days.

M.E. sumer, from O.E. sumor (cf. O.S., O.N., O.H.G. sumar, O.Fris. sumur, M.Du. somer, Du. zomer, Ger. Sommer), from PIE base *sem- "summer;" cf. Av. ham- "summer;" Mid.Pers. hāin "summer;" Skt. sámā- "half-year, season;" Arm. am "year," amarn "summer;" O.Ir. sam "summer;" O.Welsh ham "summer."

From Mid.Pers. tâpistân, ultimately from Proto-Iranain *tap-stā- "hot, heat season, time, place." The first component *tap- "to shine, radiate;" cf. Mod.Pers. tâbidan, variants tâftban "to shine," tafsidan "to become hot;" Mid.Pers. tâftan "to heat, burn, shine;" taftan "to become hot;" Parthian t'b "to shine;" Av. tāp-, taf- "to warm up, heat," tafsat "became hot," tāpaiieiti "to create warmth;" cf. Skt. tap- "to heat, be/become hot; to spoil, injure, damage; to suffer," tapati "burns;" L. tepere "to be warm," tepidus "warm;" PIE base *tep- "to be warm."
The second component *stā- "to stand; to set; to place;" a suffix of "place, land, country" and in rare cases "time;" examples: لرستان "Lorestân;" کردستان "Kurdestân;" افغانستان "Afghanistan;" ترکستان "Turkistan;" پاکستان "Pakistan;" انگلستان "England;" لهستان "Poland;" کوهستان "kuhestân = mountaneous region, highland;" تابستان "summer;" زمستان "winter." From Mid.Pers. -stân, -istân. Examples: gôstân (گاوستان) "cowshed;" šapistân (شبستان) "dormitory;" tâpistân "summer;" zamistân "winter." From O.Pers. stāna- "place;" Av. stāna-, as in gaostāna- (Mid.Pers. gôstân, as above) "cowshed;" from Proto-Iranian *stāna-. This suffix is related to O.Pers./Av. base sta- "to stand;" Mod.Pers. istâdan (ایستادن) "to stand;" cf. Skt. sthā- "to stand," sthāna- "standing;" Gk. histemi "to put, place," stasis "standing still;" L. stare "to stand;" Goth. standan; O.H.G. stantan; O.E. standan; E. stand; PIE base *sta- "to stand."

The moment in the northern hemisphere when the → Sun attains its highest → declination of 23°26' (or 23°.44) with respect the → equator plane. It happens when the Earth's axis is orientated directly toward the Sun, on 21 or 22 June. During the northern solstice the Sun appears to be directly overhead at noon for places situated at → latitude 23.44 degrees north, known as the → tropic of Cancer. The summer solstice can occur at any moment during the day. Two successive summer solstices are shifted in time by about 6 h. The summer solstice in the northern hemisphere is the → winter solstice in the southern hemisphere.

→ summer; → solstice.

The triangular shape formed by the three bright stars → Altair, → Deneb, and → Vega on the northern hemisphere's → celestial sphere, particularly visible during the summer months.

→ summer; → triangle.