It’s June 1, the first day of meteorological summer, which will last through August. We expect the season to be warmer than average overall, and the month of June will probably follow suit — to a point.

June temperatures look as though they will be slightly above average. In D.C., the month’s average temperature is 75.2 degrees. This year looks like it will end up between 75.7 and 76.2 degrees (we know — very specific, but we need to grade ourselves on this when it’s over!).

When will we hit 90 degrees?

This year has joined five others since 2000 in which May did not climb above 90 degrees. Given the cooler May, we’d typically hit 90 by June 10 — but right now, the models are not keen on that kind of heat.

June rainfall should be close to slightly above normal with a range of 3.78 inches (normal) to 4.25 inches (above normal).  The latest guidance favors picking up as much as 1 to 1½ inches of rain in just the first 10 days of the month.

June forecast rationale

El Niño gone, but atmospheric reflection lingers

The latest data on El Niño suggests it has disappeared from the Pacific. In fact, last week’s water temperatures in the key region around the equator was actually just below normal — the first cooler than average reading since July 2014.

But despite the disappearance, the atmosphere is still behaving like it exists, which is normal. It will take a while for the effects to wane. It will keep the weather somewhat active and wet over the United States for a while, and it will prevent intense heat from establishing. This means that we should be cautious about going too warm or too dry at the front of the summer.

Long-range models

The CFS model has been jumping around quite a bit for the month of June — also indicative of lingering El Niño effects. It’s showing a slightly warmer than normal forecast and slightly wetter than normal situation. I agree with this assessment based on what has been happening at the end of May and what the first half of June is looking like on other dynamic models.


National Weather Service outlook

The National Weather Service is more cautious in their forecast for June. They show no forecasts for either precipitation or temperature, which means there are “equal chances” of being warmer or cooler than average and wetter or drier than average. Given the warm start to June in the West and Southeast, along with a very wet May for Texas, they feel far more confident making forecasts for these areas. They factor soil moisture fairly heavily into their thinking — hence the cooler look for Texas and the nearby Southern Plains.


Tough May forecast review

The temperature forecast

I wrote: We favor a warmer-than-normal lean to the month, but as with April, we could see lots of volatility from day to day and week to week. May’s average temperature is 66 degrees, and we predict it will be exceeded by ½ to 2 degrees — ending anywhere from 66.5 to 68 degrees.

Reality: May’s average temperature of 63.9 was 2.1 degrees cooler than normal. The last-minute warm-up wasn’t enough to save this forecast. It was a fail thanks to the much-cooler-than-expected middle third of the month.

The rain forecast

I wrote: As noted above, the second half of the month could dry out again, so we’ll go for a cautious 3.75 to 4.25 inches, which is close to normal. If we get that range, it will be wetter than three of the past four months.

Reality: We ended up with with 5.65 inches, which is well above the normal range I offered, thanks again to a very wet pattern.

Summary review

I was somewhat correct on the variability but wrong on both temperature and precipitation directions. The spring and autumn months tend to be more variable and far less predictable than the summer months, so hopefully we’ll get on a better footing in June!

Grade: D-

What do you think?