A crypto winter for digital assets has given way to a white-hot summer.

The world’s No.1 cryptocurrency rose to its highest level in about 17 months Wednesday, extending its rally to nearly 60% in June so far.

At the day’s peak, bitcoin futures US:BTCM19 hit an intraday high on CME Group Inc. CME, +0.97% at $13,680, according to FactSet data.

Bitcoin prices BTCUSD, -0.15% on CoinDesk also were surging above $13,000. But prices tumbled more than $1,700 in a matter of minutes Wednesday, after Coinbase’s website apparently crashed. The site was back online Wednesday evening, and prices were last around $12,400.

Gains for bitcoin, the digital coin created back in 2009, have taken its market value, the total of all bitcoin’s in circulation, to $237 billion. Wednesday’s rally means that bitcoin’s value now represents 62.6% of all digital currencies tracked by data site CoinMarketCap.com. At its peak on Dec. 16, 2017, bitcoin’s market value was at $326.5 billion.

It’s unclear what has driven bitcoin’s price higher lately, but after values reached a December nadir at $3,194.96, the asset has recovered, climbing 319%.

Some market participants point to increased investment volume in bitcoin, reflecting more appetite for the cryptographic asset, as institutional investors, including traditional companies, have launched crypto-related ventures.

Michael Moro, CEO of digital currency trading platform Genesis Global Trading, said “ volumes are 2x to 3x higher than where we were 12 months ago,” in emailed comments.

“While this rise in volume has come from increased activity among our usual buyer base of hedge funds and family offices, an interesting new buyer group has emerged for us - endowments of private schools. This new group helps highlight how Bitcoin and crypto adoption is spreading,” he said.

Facebook Inc.’s FB, +0.20% proposed Libra coin will use blockchain, the digital-ledger technology that underpins cryptocurrencies like bitcoin, to create a digital currency that the social-media giant and its dozens of backers, including Uber Technologies Inc. UBER, -0.59% Visa Inc. V, +0.07% Mastercard Inc. MA, +1.13% and PayPal Holdings Inc. PYPL, +0.31% hope will evolve into a global payment system.

The move has been widely viewed as an implicit endorsement of the blockchain technology and to a lesser extent crypto assets, which were first digitally engineered more than a decade ago when a person or persons known as Satoshi Nakamoto minted the first bitcoin.

The strong rally, however, has prompted some crypto experts to call for caution by novice investors.

Jeff Dorman, the chief investment officer of crypto investment management firm Arca, told MarketWatch that bitcoin’s parabolic rise in June suggests the asset is now “overbought, and due for a fall, flashing red”.

“We look at a variety of indicators and they are all [signaling] overbought,” Dorman said.

Last week, Fundstrat’s Thomas Lee, a popular crypto bull said he believed the rip higher for bitcoin was due to investor “FOMO”, or fear of missing out. He is predicting that prices eventually will hit $40,000. To be sure, Lee made a number of wrong forecasts for bitcoin in 2018.

Year to date, bitcoin futures have gained 270%, and assets pegged to bitcoin also have jumped.

Grayscale Investments, a subsidiary of Digital Currency Group, which manages the Grayscale Bitcoin Trust GBTC, +5.27% , a popular way to bet on bitcoin, is up 325% in the first six months of 2019.

By comparison, the Dow Jones Industrial Average DJIA, -0.50% has climbed 14% so far this year, the S&P 500 index SPX, -0.28% has gained 16.5%, while the Nasdaq Composite Index COMP, +0.07% has returned 19.3% thus far in 2019, according to FactSet data as of Wednesday afternoon trade.

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