ING's strategists note that an old financial market adage "Sell in May and go away" suggests that investors take a more conservative approach to risk during the summer months. 

"Whether it applies this year remains to be seen, although for reference the S&P 500 has rallied in seven of the last eight years during the May-October period for an average gain of 4%."

"What may concern investors today, however, is that market favourites such as Amazon and Apple (stocks that have led the 35% rally from the lows in S&P 500) struggled to provide guidance when releasing 1Q earnings yesterday. Apple did not provide a forecast for the first time in 10 years, while Amazon gave a 2Q profit forecast of anywhere between a $1.5 billion profit and a $1.5 billion loss."

With the S&P 500 seemingly stalling at a 62% technical retracement of the February-March sell-off and the market perhaps too conservative in only looking for a 20% fall in S&P 500 earnings this year, it looks as though investors will take a cautious attitude to risk."

"Thus, it may be too early to expect the kind of benign environment that can allow the dollar to sink across the board."

"For today, the US data calendar will see April ISM manufacturing, expected to drop back to the lows seen in December 2008. DXY could move back into a 99.00-99.50 trading range."