We’ve seen an uptick in IPO activity in recent weeks, with two Seattle companies (Zillow.com and Impinj) deciding to take the plunge. Those filings appear to be part of a larger national trend. So far this month, 31 companies have filed to go public, the most active month in nearly four years, according to an analysis out this week from Renaissance Capital’s IPO Home.

The crop includes retailers, online content firms and renewable energy companies.

And the filings come on top of a strong month for priced IPOs. So far, 21 companies have raised $5.6 billion, with the average return up 18 percent, according to Renaissance Capital.

That’s good news for companies looking to hit the IPO jackpot at the right time. But, as we’ve noted last week, it will be interesting to see how the market reacts to Impinj and Zillow (both of which have under $35 million in annual revenue and posted losses last year).

Will the window stay open for them?

Previously on GeekWire: Zillow, Impinj and why Seattle needs a new crop of IPOs

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