When Did It Rain Last Night?

When you woke up this morning, you noticed that the ground and especially the pavement was wet. So you would have concluded that it rained last night. However, if you had a rain gage, you would have seen that it was bone dry. Where did the water come from?

The record breaking warm air mass with brisk southerly breezes was the key. Temperatures overnight were near record levels and the dew point was only about 5 degrees cooler. This meant that the pavement was cooler than the dew point, so dew formed. Normally, in this situation dense fog would have formed like it did earlier this week. However, the southerly winds were too strong to let that happen, and in fact, dried out many elevated surfaces. Thus, mainly the pavement was wet.

Above is a photo of the NWS driveway taken this morning. You can see the wet pavement including some small puddles toward the right. The shrub on the left was dry.

Numerous temperature records will be broken today, both warm minimums as well as warm maximums.