Speaking during a visit to the flood-hit town of Matlock in Derbyshire on Friday night, Mr Johnson said the government will "certainly stand by ready to help" after the country was hit by deluge of downpours described as "almost biblical".
The Prime Minister's visit came after the death of a woman who was reportedly swept away by floodwater as parts of the Midlands and northern England were battered by a month's worth of rain in one day.
The body of the woman, who has not been identified, was recovered in Darley Dale, near Matlock, on Friday morning after being swept away in the nearby village of Rowsley.
Asked what the government was doing to support people during floods, Mr Johnson said: "We've got a huge programme of flood defences and flood preparation - there's £2.6 billion going into it and I think £50 million has gone into Derbyshire alone.
"But in the end, you've got to face the reality that places like this are vulnerable to flooding - we're going to see more of it.
"So we're going to rely on local authorities to do the excellent job they have done here in this situation and we're going to rely on the emergency services and also prepare for the next event.
"The crucial thing is to put in the preparations and that's what we're doing."
Swineshaw in the Peak District saw 112mm of rainfall during Thursday - the highest total of anywhere across England - while flood-hit parts of Sheffield experienced 85mm during the same period.
The average monthly rainfall total for Yorkshire at this time of year is 89mm.
Addressing what support was on offer for those whose homes or businesses had flooded on Friday, Mr Johnson said: "It's businesses particularly who deserve our sympathies and they've had a really tough time.
"You cannot underestimate the psychological effect of flooding on people - it is a big, big blow.
"People have been moved out of their homes and probably hundreds of businesses have seen damage to their properties - we stand ready to help in any way that we can.
"We are seeing more and more serious flooding - perhaps because of building, almost certainly because of climate change - we need to prepare and we need to be investing in those defences and that's what this government is doing."
Residents in Toll Bar, near Doncaster, described Thursday's downpour as "almost biblical" while others made comparisons with deluges which devastated communities in the summer of 2007.
Pressed on whether he could be more specific in what help would be available, the Prime Minister said: "Nadhim Zahawi, the business minister, is ready to help small businesses in any way that they need to get back on their feet - whether it's loans or particular support they need for the short term to do with flood damage they have sustained.
"At the moment, touch wood, this is not looking like something that we need to escalate to the level of a national emergency but we certainly stand by ready to help small businesses in any way that we can."