NOAA's National Centers for Environmental Information
Note: This Synoptic Discussion describes recent weather events and climate anomalies in relation to the phenomena that cause the weather. These phenomena include the jet stream, fronts and low pressure systems that bring precipitation, high pressure systems that bring dry weather, and the mechanisms which control these features — such as El Niño, La Niña, and other oceanic and atmospheric drivers (PNA, NAO, AO, and others). The report may contain more technical language than other components of the State of the Climate series.
Summary
The contiguous U.S. climate was dominated by broad ridging throughout much of the country during most of 2024. This pattern was observed as a strong El Niño observed during the beginning of the year transitioned to a neutral phase throughout the remainder of the year. Throughout the year, near record to record level warmth was observed. A strongly positive WPO and EPO was observed throughout much of 2024, and these teleconnections likely influenced the very warm temperatures observed throughout the year. Precipitation totals were above normal over the continental U.S. during 2024, though the precipitation varied greatly across the year due to shorter term synoptic patterns.
Atmospheric Drivers
- January
- El Niño
- Positive North Atlantic Oscillation (NAO)
- February
- El Niño
- Positive Arctic Oscillation (AO)
- Positive NAO
- Positive West Pacific Oscillation (WPO)
- March
- El Niño
- Negative AO
- Positive WPO
- April
- El Niño
- Positive AO
- Negative NAO
- May
- Negative Pacific/North American (PNA) pattern
- Positive WPO
- Positive East Pacific Oscillation (EPO)
- June
- Positive PNA
- Positive WPO
- Positive EPO
- July
- Positive AO
- Positive NAO
- Positive PNA
- Positive WPO
- August
- Positive AO
- Positive NAO
- Negative PNA
- Positive WPO
- September
- Negative AO
- Negative NAO
- Positive PNA
- Positive WPO
- Positive EPO
- October
- Positive EPO
- November
- Negative WPO
- December
- La Niña
- Positive NAO
- Positive PNA
Seasonal Evolution
January-March
The North American circulation at the beginning of 2024 was dominated by the effects of El Niño. The beginning of 2024 saw a broad ridging pattern over the eastern U.S. extending into Canada, with troughing over the Southwest. As a result, much warmer than normal conditions were experienced across most of the Northeast and Midwest regions during the first few months of the year. The Northeast coastline also experienced wetter than normal conditions during the early part of 2024.
April-June
The El Niño conditions observed during the early part of 2024 rapidly weakened, and by April to June had transitioned into a neutral phase. Throughout April to June a strong positive EPO and WPO was observed. Alongside the positive EPO and WPO, temperatures across most of the continental U.S. were well above average with many states experiencing near record warmth for the period. This was continuing with the trend of above average temperatures being experienced throughout most of the country for the first half of the year.
June-August
During June through August, there was broad but relatively weak ridging across most of the U.S. This corresponded with warmer than normal temperatures over most of the country, with the exception of the northern Plains, which saw more seasonal temperatures. During this period there was a strong positive WPO and AO, which may have influenced the warmer than normal temperatures seen over parts of the country. Additionally, the Northeast and Midwest regions saw enhanced precipitation during this period.
August-October
From August through October, a very strong ridge dominated most of the continental U.S., which corresponded to record high temperatures across many states (particularly over the Rockies). Near record temperatures were observed across most of the western and central U.S., with the eastern U.S. also experiencing above average temperatures. A strongly positive WPO was observed throughout this period, which likely influenced the broad ridging across the central U.S. The broad ridging also led to below average precipitation across most of the country during this period, with above average precipitation being observed only in parts of the Southeast from Florida through to North Carolina due to the impacts of Hurricane Helene and Hurricane Milton.
October-December
At the end of 2024 the broad ridging that had dominated the U.S. continued, which was associated with near record to record levels of warmth across most of the U.S. Record warmth was observed over the southern Plains and Texas during the end of the year. The Niño 3.4 temperatures continued to drop during this period and by December bordered on a weak La Niña. There was also a positive EPO observed during the end of the year as well, which likely influenced the warmer than normal temperatures observed across much of the country.