European model shows a pool of cold air over the region Sunday evening. (WeatherBell.com)

This miserable May, if it’s not one thing, it’s another.

While our rainy-day streak may finally end Sunday, temperatures will then turn considerably cooler than normal even when the sun returns.

The chilly weather this month is an emerging story, previously trumped by all the clouds and rain.

Temperatures on all but two days this May have fallen shy of average. On three days highs only reached the 50s, tying for ninth most on record (month-to-date).

Not once has it hit 80. And the average temperature for the month, in its entirety, is running 4 degrees below normal.

At this time last May, 11 of 12 days had reached at least 80 and one of those days even soared to 90. We had pronounced spring over and summer started. (It ended up as the warmest May on record.)

Summer shouldn’t be on anyone’s radar screen yet, as we have some more very chilly air with respect to normal on the way.

On Saturday, a strong cold front (accompanied by rain, of course) barges through the region. By Sunday morning, temperatures tumble into the mid-to-upper 40s.


Temperature difference from average forecast Saturday and Sunday (WeatherBell.com)

While mid-40s in mid-May are chilly, they’re not quite record-challenging — Sunday’s record low is 40. They’re also not particularly uncommon. Lows below 50 occur on about 20 percent of mornings at this time of year.


Low temperatures forecast by National Weather Service for Sunday morning. (WeatherBell.com)

But the coldest air from this late spring cool snap may not arrive until early Monday.

Following highs Sunday afternoon in the low-to-mid 60s, some 10 to 15 degrees below normal, temperatures may fall steeply overnight.

By Monday morning, lows could dip into the 30s in the coldest parts of the D.C. metro region. A bit of patchy frost cannot even be ruled out if skies stay clear and winds are light. The GFS model forecasts near-record lows in the mid-30s but often has a cold bias. The European model (not shown) predicts more realistic lows of 40-45.


GFS model predicts lows in the 30s next Monday. BRRR! (StormVistaWxModels.com)

After that cold start, Monday afternoon’s temperatures remain below normal, with highs in the 60s, despite sunshine.

For a true taste of winter Sunday and Monday, head to the high terrain (above 3,500 to 4,000 feet) of West Virginia and western Maryland. Some wet snow is possible there early Sunday along with below freezing temperatures Sunday night. Note that in parts of this area, the average last freeze isn’t until around June 1.


GFS model simulates some snow in the high terrain of West Virginia and western Maryland early Sunday. (WeatherBell.com)

The weather for the middle of next week is a toss-up. The GFS model shows temperatures near normal while the European model shows highs, again, only in the 50s. Either way, another wet period is likely to commence. If it’s not one thing, it’s another.