The new data have been released by EU border agency Frontex.
At the same time France and Britain have announced they will sign a deal on a plan to tackle the crisis in the French port of Calais.
Thousands of migrants have attempted to reach the UK through the Channel Tunnel from makeshift camps around the northern French city.
The United Nations says 21,000 migrants have arrived in Greece in the past week alone.
Arriving on the island of Kos, Syrian refugee Salah has asked for compassion, saying he just wants to be treated with humanity.
"I want to live like any human, like any man, any people, with freedom."
Germany says it could receive as many as 750,000 asylum-seekers this year.
The increase from its previous estimate of 450,000 is the latest sign of the scale of the crisis.
German Chancellor Angela Merkel describes it as a bigger challenge for Europe than Greece's debt crisis.
Greece is feeling the strain of both, but the UNHCR's William Spindler says Greece has a responsibility to do more.
"If the central authority would come up with a leadership ambition and appoint somebody who would coordinate this response, then we and other international organisations would be ready to come and help. But it is difficult for us, if there is, to start working on the ground if we don't have somebody who is in charge."
UNHCR spokeswoman Stella Nanou says Greece must be supported by the European Union.
"So these high numbers, in combination with the lack of appropriate reception infrastructure and very slow registration procedures, has led to this situation that as UNHCR we've called a humanitarian emergency that has to be addressed as soon as possible."
The perils of the boat journey across the Mediterreanean were again brought to light when at least 40 migrants died in the hold of an overcrowded smuggling boat in the Sea north of Libya.
Italian rescuers say it appears they suffocated on fuel fumes.
More than 240,000 migrants have made the crossing already this year, fleeing conflicts in sub-Saharan Africa and the Middle East.
The International Organisation for Migration's Joel Millman says more than 1,000 people a day are being rescued on their way to Italy and Greece.
"Migrants are being rescued, both in Italy and Greece, at a rate of over a thousand a day if you add the two nations together and we would like to point out that there are 135 days left this year, we have every expectation that the total number of arrivals will surpass 300,000."
Last month, EU member states agreed to take in 32,000 of the asylum seekers arriving in Italy and Greece over the next two years.
Australia's annual refugee intake is currently just under 14,000.
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