There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
sachwen
noun. summer, midsummer
saiwen
noun. summer, midsummer
aust
noun. summer
ost
noun. summer
safwen
noun. summer
aust
noun. summer
awest
noun. summer
aurinde
noun. summer, pleasant warmth
austa
noun. (high) summer
avesta
noun. summer
saiwali
noun. summer
laire
noun. summer
úrien
proper name. Summer
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
Ellairë
summer
Ellairë alternative name of June (PM:135); evidently incorporating lairë "summer"; the el- part is probably an assimilated form of er-, an element meaning one or first, June being the first summer month.
lairë
summer
lairë (1) noun "summer" (Letters:283, VT45:26), in the calendar of Imladris a precisely defined period of 72 days, but also used without any exact definition (Appendix D). Oiolairë "Eversummer", name of a tree (UT:167), see also Coron Oiolairë. Lairelossë noun *"Summer-snow", name of a tree (UT:167), perhaps with white flowers.
laire
noun. summer
lairë
noun. summer
loer
noun. summer
lairē
noun. *summer
laer
noun. summer
laer
summer
laer (no distinct pl. form). Note: a homophone means ”song”.
laer
summer
(no distinct pl. form). Note: a homophone means ”song”.
Another name for laire “summer” in drafts of the Lord of the Rings appendices (PM/134). Its initial element seems to be Ûr “Sun”.