Mary Shelley notes in her Journal entry for May-June-July 1833:

May -- June -- July -- Harrow

Three happy Months -- varied yet delightful -- the weather is beautiful -- the only genial spring I ever knew opened on us on May 4th - the birds -- the cuckoo & Nightingales -- are numerous -- the tender young green mantles the earth with beauty --

I was taken ill with the Influe[n]za again June 9 -- & suffered greatly being confined to my bed for ten days -- myconvalescence -- as ever with this vile illness -- slow & painful -- Julia [Robinson] spends the month of July with me. (529-530)

[See the year 1833 in the Mary Shelley Chronology.]