crisa -cis- gismu

x1 is summer/summertime [hot season] of year x2 at location x3.

See also citsi, critu, dunra, vensa.

In notes:

citsi
x1 is a season/is seasonal [cyclical interval], defined by interval/property x2, of year(s) x3.
critu
x1 is autumn/fall [harvest/cooling season] of year x2 at location x3.
dunra
x1 is winter/wintertime [cold season] of year x2 at location x3.
vensa
x1 is spring/springtime [warming season] of year x2 at location x3; (adjective:) x1 is vernal.
crisaunra
x1 is Summer(time)/(a)estival [hot season] in the northern hemisphere and Winter(time)/hibernal/hiemal [cold season] in the southern hemisphere of year x2 and for celestial body x3.
dunraisa
x1 is Summer(time)/(a)estival [hot season] in the southern hemisphere and Winter(time)/hibernal/hiemal [cold season] in the northern hemisphere of year x2 and for celestial body x3.