Traffic Predict
How Rain Slows Freeway Traffic
Freeway traffic slows down in the rain everywhere, but not by the same amount. Across 8 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 |
|---|---|---|---|---|---|
| Bakersfield | −2% | −4% | – | – | 305 |
| Fresno | −3% | −5% | −8% | – | 352 |
| Sacramento | −2% | −6% | −6% | – | 501 |
| Bay Area | −3% | −6% | −7% | – | 569 |
| Los Angeles | −2% | −6% | −5% | 1.0× | 371 |
| Inland Empire | −2% | −6% | −9% | – | 324 |
| Orange County | −2% | −7% | −8% | – | 331 |
| San Diego | −4% | −9% | −10% | 1.4× | 397 |
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.
Bakersfield
In the rain, freeways in Bakersfield average 2% slower than on a dry day at the same time; at the weekday evening rush, from 62 mph to 60 mph. 8% 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% | −6% | – | −2% |
| Weekday midday (10 am–3 pm) | −2% | −6% | – | −2% |
| Weekday evening rush (3–7 pm) | −3% | −4% | – | −3% |
| Weekend daytime (6 am–7 pm) | −2% | −4% | – | −2% |
| Night (7 pm–6 am) | −1% | −3% | – | −2% |
| All hours | −2% | −4% | – | −2% |
Change in average speed vs dry days. Based on 305 storm days (Jan 2017 to Oct 2026) and 12,414 freeway-direction hours of rain; – means too few rainy hours to say.
Bakersfield traffic right now · Is Bakersfield traffic getting worse?
Fresno
In the rain, freeways in Fresno average 3% slower than on a dry day at the same time; at the weekday evening rush, from 61 mph to 58 mph. 8% 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% | −6% | – | −3% |
| Weekday midday (10 am–3 pm) | −3% | −5% | – | −3% |
| Weekday evening rush (3–7 pm) | −5% | −8% | – | −5% |
| Weekend daytime (6 am–7 pm) | −3% | −4% | – | −3% |
| Night (7 pm–6 am) | −2% | −3% | – | −2% |
| All hours | −3% | −5% | −8% | −3% |
Change in average speed vs dry days. Based on 352 storm days (Jan 2017 to Dec 2025) and 15,478 freeway-direction hours of rain; – means too few rainy hours to say.
Fresno traffic right now · Is Fresno traffic getting worse?
Sacramento
In the rain, freeways in Sacramento average 2% slower than on a dry day at the same time; at the weekday evening rush, from 58 mph to 57 mph. 8% 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% | −3% | −3% |
| Weekday midday (10 am–3 pm) | −2% | −7% | −9% | −3% |
| Weekday evening rush (3–7 pm) | −2% | −8% | – | −3% |
| Weekend daytime (6 am–7 pm) | −1% | −5% | −8% | −2% |
| Night (7 pm–6 am) | −1% | −3% | −3% | −2% |
| All hours | −2% | −6% | −6% | −2% |
Change in average speed vs dry days. Based on 501 storm days (Jan 2017 to Dec 2025) and 61,166 freeway-direction hours of rain; – means too few rainy hours to say.
Sacramento traffic right now · Is Sacramento traffic getting worse?
Bay Area
In the rain, freeways in the San Francisco Bay Area average 3% slower than on a dry day at the same time; at the weekday evening rush, from 57 mph to 55 mph. 6% 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% | −6% | −5% | −3% |
| Weekday midday (10 am–3 pm) | −3% | −6% | −6% | −3% |
| Weekday evening rush (3–7 pm) | −2% | −6% | −9% | −3% |
| Weekend daytime (6 am–7 pm) | −2% | −6% | −9% | −2% |
| Night (7 pm–6 am) | −3% | −5% | −6% | −3% |
| All hours | −3% | −6% | −7% | −3% |
Change in average speed vs dry days. Based on 569 storm days (Jan 2017 to Sep 2026) and 176,515 freeway-direction hours of rain; – means too few rainy hours to say.
Bay Area traffic right now · Is Bay Area traffic getting worse?
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) | −2% | −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 371 storm days (Jan 2017 to Dec 2025) and 85,089 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 3% slower than on a dry day at the same time; at the weekday evening rush, from 56 mph to 54 mph. 8% 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% | −6% | −8% | −3% |
| Weekday midday (10 am–3 pm) | −3% | −8% | −10% | −4% |
| Weekday evening rush (3–7 pm) | −3% | −7% | −11% | −3% |
| Weekend daytime (6 am–7 pm) | −2% | −5% | −8% | −2% |
| Night (7 pm–6 am) | −2% | −5% | −7% | −3% |
| All hours | −2% | −6% | −9% | −3% |
Change in average speed vs dry days. Based on 324 storm days (Jan 2017 to Oct 2026) and 28,364 freeway-direction hours of rain; – means too few rainy hours to say.
Inland Empire traffic right now · Is Inland Empire traffic getting worse?
Orange County
In the rain, freeways in Orange County average 3% slower than on a dry day at the same time; at the weekday evening rush, from 55 mph to 54 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% | −3% |
| Weekday midday (10 am–3 pm) | −3% | −10% | −10% | −4% |
| Weekday evening rush (3–7 pm) | −2% | −7% | −11% | −3% |
| Weekend daytime (6 am–7 pm) | −1% | −6% | −6% | −2% |
| Night (7 pm–6 am) | −3% | −5% | −5% | −3% |
| All hours | −2% | −7% | −8% | −3% |
Change in average speed vs dry days. Based on 331 storm days (Jan 2017 to Oct 2026) and 56,893 freeway-direction hours of rain; – means too few rainy hours to say.
Orange County traffic right now · Is Orange County traffic getting worse?
San Diego
In the rain, freeways in San Diego average 4% slower than on a dry day at the same time; at the weekday evening rush, from 56 mph to 54 mph. 10% 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) | −4% | −9% | −8% | −4% |
| Weekday midday (10 am–3 pm) | −4% | −12% | −12% | −5% |
| Weekday evening rush (3–7 pm) | −4% | −9% | −11% | −4% |
| Weekend daytime (6 am–7 pm) | −3% | −8% | −12% | −4% |
| Night (7 pm–6 am) | −3% | −6% | −10% | −4% |
| All hours | −4% | −9% | −10% | −4% |
Change in average speed vs dry days. Based on 397 storm days (Jan 2017 to Dec 2025) and 53,352 freeway-direction hours of rain; – means too few rainy hours to say.
San Diego traffic right now · Is San Diego traffic getting worse?
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.