🇺🇸 Allentown vs 🇺🇸 San Francisco

Allentown in the Lehigh Valley south of the Blue Mountain Ridge has a sheltered climate with less precipitation than the coastal plain. The Blue Mountain blocks some northwesterly cold air creating slightly milder conditions. The Lehigh River creates valley humidity and the dense urban core has significant heat island effects.

San Francisco's climate is shaped by its position on a peninsula surrounded by the Pacific Ocean and San Francisco Bay. The coastal fog (Karl the Fog) rolls in through the Golden Gate each summer afternoon, keeping temperatures mild year-round. The city has dramatically different microclimates — the Sunset District fog-bound while the Mission basks in sun on the same day.