The much missed sun has at last broken a spell of rainy days here in Hanoi. In sympathy with the change of weather, my own heath has arisen from its own spell under the flu. For those reasons, I am once again able to enjoy my daily walks. Alas, boiling heat overwhelms us if we dare to step outside, so we appreciate air conditioning more than ever.
"Alas" is better than "however" because "alas" conveys disappointment, whereas "however" only conveys logic.