Washingtonians have had it good this March. Temperatures have averaged seven degrees warmer than normal, and highs have reached at least 60 degrees on 21 of 30 days.
The first and perhaps most potent front will sweep through the region Saturday night. Forecast highs Sunday, depending on the model, range from the upper 40s to mid-50s — roughly 10 degrees below normal. Gusty winds out of the northwest will make it feel even colder.
Sunday night into Monday morning, lows have a chance to approach freezing inside the Beltway and dip into the 20s in our normally colder areas, as they did this morning (Dulles hit 27 degrees).
The cold next week will come in brief punches, flanked by milder weather in between.
Models suggest moderate temperatures Monday but then a second cold front passing through at night bringing another shot of chilly air for Tuesday. Temperatures may try to mount another comeback Wednesday and Thursday before a third cold front knocks them back down toward the end of the week. (Note that there is some uncertainty in this timing and it is likely to change some.)
In other words, next week promises to be a bit of a roller coaster. With the parade of cold fronts, there may be multiple nights in which temperatures flirt with freezing, especially in our colder areas north and west of town.
These temperatures could pose some challenges for gardeners after the very mild March kickstarted the growing season.
“Warmth has caused many plants to begin growing significantly earlier than normal . . . and has also encouraged early planting,” the National Weather Service said in a special advisory posted Tuesday. “Reports from our agricultural partners indicate fruit trees are starting to bloom in many areas . . . and some crops normally reserved for April planting are already being planted.”
The Weather Service said it will issue frost and freeze products, as necessary, next week — potentially initiating them more than 10 days ahead of schedule.
“Normally . . . these areas would not receive frost and freeze products until April 11th,” the Weather Service advisory said. “. . . But the unusual warmth requires an earlier start to these products to ensure protective measures are taken.”
The average date of the last freeze at Reagan National Airport is March 28. Temperatures there could flirt with freezing Monday morning, but my hunch is that they will remain in the mid- to upper 30s.
The area around Dulles Airport is much more likely to see freezing temperatures next week. The average date of the last freeze there is April 21.
While next week is very likely to feature some cooler-than-normal weather, models are hinting at a more stable and mild regime returning to the region around April 10.
But even so, that is not to say the region will be clear of freezing temperatures beyond that point. Since 1981, National Airport has recorded a freeze as late as April 13 and Dulles as late as May 22.
If you live in colder areas outside the Beltway, the old rule of thumb to hold off until Mother’s Day to plant annuals is a good idea.