After back-to-back chilly months, it appears that May will finally turn the corner. At last, spring is here.
We get a big head-start on a warmer-than-normal month this week with temperatures in the 80s and perhaps the first 90-degree day of the year. It’s harder to make a call on rain in May — it looks as if the month will start drier than normal, but we’ll have a higher chance of rain later in the month.
May outlook
Temperature: 68 to 70 degrees; the warmest since 2015 (normal: 66 degrees).
Rain: Near to below normal at 2 to 4 inches, the driest since 2015 (normal: 3.99 inches).
Extremes: The warmest May temperature was set May 31, 1991, at 99, and the coolest was in 1906, when the low reached 33 on May 11. We don’t expect to break either of those records at this point.
The thinking behind our outlook
It has been the slowest start to spring since 1999, but things are finally looking up. It looks as if May will be warmer than normal. The early-month surge of significant warmth arrives this week with highs in the 80s and perhaps a day or two in the 90s. Humidity isn’t at summer levels — yet.
The heat isn’t going to stick around — assuming the weekend cold front arrives on schedule — but we should continue to see intermittent waves of warmth to remind us that summer is near.
Here’s this week’s warm surge on a recent European modeling run. Warm colors represent ridges, and blue colors represent troughs. As you can see, the model expects a strong ridge to develop over the Eastern Seaboard this week.
Looking back through the weather history books, La Niña appears to give D.C. a chilly March-April, followed by a warm May, which is exactly what we’ve seen this year. La Niña, which is a cooling of the tropical Pacific Ocean, is currently fading away, but we are still experiencing lingering effects globally that favor a warmer May in Washington. It could also lead to a hot June before cooler El Niño influences arrive later this summer.
Every month this year has flipped from dry to wet and back. January and March were dry; February and April were wet. Based on that pattern, we’re due for a drier month in May, and the first two weeks of the month are looking that way.
The Washington region is still in drought conditions, but we expect improvement to this map in its Thursday update. However, I suspect at least abnormally dry conditions may expand again over the next two weeks.
The NOAA CFS model performed well when it predicted a cool April. It has been fairly consistent on a warm May with about-normal rainfall. The weekly outlooks from the CFS (and the Europeans) show plenty of back and forth, though. This week’s warmth should be offset by cooling next week, but another round of warmth will hit by the third week.
Overall, we think the warm weather will win out.