Traffic Predict
How Rain Slows Freeway Traffic
Freeway traffic slows down in the rain everywhere, but not by the same amount. Across 3 cities and every storm we have measured since 2017, we compared each rainy hour with the same freeway at the same time on dry days.
City by city
| City | Light rain | Moderate rain | Heavy rain | Delay in rain vs dry | Storm days |
|---|---|---|---|---|---|
| Los Angeles | −2% | −6% | −5% | 1.0× | 350 |
| Inland Empire | −2% | −8% | – | – | 65 |
| Orange County | −3% | −8% | −12% | 1.0× | 255 |
Change in average freeway speed compared with dry days at the same time, all hours. Light rain is under 2.5 mm (0.1 inch) an hour, heavy rain 7.6 mm (0.3 inch) or more. Delay is time lost below 35 mph per mile driven. Cities are ordered from the smallest slowdown in moderate rain to the largest.
Los Angeles
In the rain, freeways in Los Angeles average 3% slower than on a dry day at the same time; at the weekday evening rush, from 51 mph to 49 mph. 7% fewer vehicles are on the road than in dry weather.
| Time | Light rain | Moderate rain | Heavy rain | Any rain |
|---|---|---|---|---|
| Weekday morning rush (6–10 am) | −3% | −7% | −5% | −4% |
| Weekday midday (10 am–3 pm) | −2% | −8% | −8% | −4% |
| Weekday evening rush (3–7 pm) | −1% | −6% | −7% | −2% |
| Weekend daytime (6 am–7 pm) | no change | −4% | −5% | −2% |
| Night (7 pm–6 am) | −2% | −5% | −4% | −3% |
| All hours | −2% | −6% | −5% | −3% |
Change in average speed vs dry days. Based on 350 storm days (Jan 2017 to Dec 2025) and 84,082 freeway-direction hours of rain; – means too few rainy hours to say.
Los Angeles traffic right now · Is Los Angeles traffic getting worse?
Inland Empire
In the rain, freeways in the Inland Empire average 2% slower than on a dry day at the same time. 12% fewer vehicles are on the road than in dry weather.
| Time | Light rain | Moderate rain | Heavy rain | Any rain |
|---|---|---|---|---|
| Weekday morning rush (6–10 am) | no change | – | – | no change |
| Weekday midday (10 am–3 pm) | −6% | – | – | −6% |
| Weekday evening rush (3–7 pm) | – | – | – | – |
| Weekend daytime (6 am–7 pm) | −4% | – | – | −4% |
| Night (7 pm–6 am) | −2% | −8% | – | −2% |
| All hours | −2% | −8% | – | −2% |
Change in average speed vs dry days. Based on 65 storm days (Jan 2017 to Dec 2025) and 646 freeway-direction hours of rain; – means too few rainy hours to say.
Inland Empire traffic right now
Orange County
In the rain, freeways in Orange County average 4% slower than on a dry day at the same time; at the weekday evening rush, from 53 mph to 51 mph. 7% fewer vehicles are on the road than in dry weather.
| Time | Light rain | Moderate rain | Heavy rain | Any rain |
|---|---|---|---|---|
| Weekday morning rush (6–10 am) | −2% | −9% | – | −3% |
| Weekday midday (10 am–3 pm) | −4% | −9% | – | −5% |
| Weekday evening rush (3–7 pm) | −4% | −9% | – | −5% |
| Weekend daytime (6 am–7 pm) | −3% | −8% | – | −4% |
| Night (7 pm–6 am) | −3% | −5% | −7% | −3% |
| All hours | −3% | −8% | −12% | −4% |
Change in average speed vs dry days. Based on 255 storm days (Jan 2017 to Dec 2025) and 9,220 freeway-direction hours of rain; – means too few rainy hours to say.
Orange County traffic right now
How this is measured
For every hour it rained on a freeway, we compare the traffic with the same freeway direction at the same hour and day of the week, one to four weeks earlier and later, on days without rain. That keeps the season, the time of day and the road the same, so the difference is the rain. Rain comes from weather radar and the Iowa Environmental Mesonet's hourly rain analysis, averaged along each freeway; dry days are checked against airport rain gauges. Holidays, and hours when many road sensors stopped reporting, are left out. Traffic: Caltrans PeMS and state road sensors. Rain: NOAA/National Weather Service radar via the Iowa Environmental Mesonet.
See also: traffic trend reports and the live map, which shows when rain is slowing a road right now.