Mostly clear,rain likely tomorrow
NWS, the American and the European model put Diamond Bar's high today between 88° and 93°, a 6° split. Tomorrow looks heavy drizzle around 79°, with a 98% chance of rain.
Diamond Bar, CA is at its warmest in Jul (average highs near 94°F) and coldest in Feb (lows around 44°F), with roughly 31 in of precipitation across the year. Below, compare what NWS, American, European forecast for Diamond Bar right now, and see exactly where they disagree.
We grade every model against the weather that actually happened, so you can see which forecast model is most accurate in United States before you trust any single number.
The CheckWeather Score blends temperature, wind and rain accuracy — each measured against ERA5 (the recorded weather) over the last 30 days across 1999 cities. Lower error means a higher score. See which forecast model is most accurate in United States, how we measure forecast accuracy, or which model each weather app uses.
The models often agree on temperature and still split on rain — and rain is usually what decides whether a plan survives. A wide rain range means the shower is genuinely uncertain, not that the forecast is wrong.