[historyteach]

From NAMI:

In about 1/10th of cases, annual relapse occurs in the summer rather than winter, possibly in response to high heat and humidity. During that period, the depression is more likely to be characterized by insomnia, decreased appetite, weight loss, and agitation or anxiety. Patients with such "reverse SAD" often find relief with summer trips to cooler climates in the north. Generally, normal air conditioning is not sufficient to relieve this depression, and an antidepressant may be needed.

In still fewer cases, a patient may experience both winter and summer depressions, while feeling fine each fall and spring, around the equinoxes.

NAMI | Seasonal Affective Disorder (SAD)

And here's a great article by the NY Times, just on the reverse SAD.
Seasonal Depression Can Accompany Summer Sun - New York Times

Hope this helps.

Shalom!