The basics: A retrograde occurs when a planet appears to be moving backwards from our vantage point here on Earth. It isn't actually moving backwards, it just appears that way. Mercury turns retrograde most often because it's nearest to us, about 3-4 times per year, and lasts for several weeks. When a planet retrogrades, what that planet rules tends to be thrown off, along with what the sign it's retrograding in rules.
With Mercury retrograde, we experience a shadow and a storm. The shadow period starts when Mercury first hits the point in the zodiac it will turn direct at, and ends when it last hits the point in the zodiac it will turn retrograde at. Most people don't feel the effects of Mercury retrograde until it enters the storm period though.
The storm period of Mercury retrograde is when Mercury is moving at its slowest, less than 40 minutes per day. Mercury is a fast-moving planet and hates it when he's moving slowly. There's usually two storm periods, one around the time Mercury turns retrograde, and one around when it turns direct.
The shadow of this Mercury retrograde begins May 22nd and lasts through July 15th. The exact retrograde begins June 7th at 7:56AM ET and ends July 1st at 8:50AM ET.
We usually have two storm periods, one around the turn retrograde and one around the turn direct, but we'll just have one long storm period for this retrograde, lasting from May 30th through July 9th. This will be an unrelenting retrograde!
Though we are finally at the end of the retrograde train, one we've been on since mid-December of last year with Venus, then Mercury, then Mars, and now Mercury again retrograding. We're almost through!
This retrograde begins in Cancer, and Cancer rules the home and family. We can see issues come up with families, related to the housing market, or (to look on the brighter side) a return to a strong housing market. We can see news with real estate in general. We may feel we need to be more connected to our families and overcompensate, or take this as a chance to reconnect with old relatives.
Conversely, we can drift further away from our families. It's a good time to do renovations and remodeling to homes and communities, or to move back to areas we've lived before.
Cancer is ruler of our emotions, and we could be impacted on a deeper level emotionally by what happens, and it shakes us to our core. Our inner foundation isn't as strong as we thought it was, but we hide our insecurity and emotional turmoil as much as we can.
Cancer rules our countries, and we can see domestic issues arise, though hopefully no attack since Jupiter is still in Cancer. We can be less supportive and nurturing, isolating each other.
Mercury retrogrades backward into air sign Gemini on June 17th at 6:07AM. Gemini is a sign that's naturally ruled by Mercury, so we could really see the Mercury troubles amplified. We have a hard time communicating with one another and understanding each other. We get bad news or misinformation. We share our ideas and they get shot down, or we keep good ideas to ourselves and they get wasted.
Gemini is ruler of the mind, and we go from trouble with our emotions to trouble with our minds. We can't come up with the new ideas we need or make the plans that will help us or get the information we need to solve the problem. This is a good time for any re-doing of mental work: revising, reviewing, editing galore. Give yourself the chance to revise your written work, and if you can, go back and redo old projects for a fresher perspective.
Gemini also rules learning, so we could see some issues with schools or education. Gemini rules young people, and we could see some trouble with them. Gemini rules communities, neighbors, and siblings, and we could have problems with them.
The turn retrograde begins at 3 degrees Cancer, so those of you Cancers born June 23rd - 26th may feel the turn retrograde most. The turn direct occurs at 24 degrees Gemini, so those of you Geminis born June 14th - 17th may feel the turn direct most.
For the rest of you, check the house(s) Mercury will be retrograding in of your own natal chart, and any aspects Mercury will make during its retrograde to your natal planets, to fully understand how it will impact you personally.
If you have Mercury retrograde in your natal or progressed chart, you may not feel the worst of this. Those individuals generally don't experience the difficulties of the retrograde because it feels more natural to them. Of course, chances are everyone else around them doesn't have the same aspect, so they can still experience difficulties brought on by others.
Suggested Reading: The Mercury. Venus and Mars Retrogrades page for general interpretations