September was once again a warmer than average month statewide. This was especially true across eastern Washington where prolonged warm spells with particularly warm overnight temperatures led to anomalies of around 5-8°F above normal. In western Washington, a brief single-day heat wave occurred on the 16th as a strong ridge built over the region. This warm day is clearly visible as a mid-month spike on the above graph of SeaTac’s daily temperatures.
