September has a reputation for being the worst month for stocks, mainly due to a messy mix of seasonal investor behavior and institutional selling, but that market swoon often creates promising long-term buying opportunities. Investors who can tune out the near-term noise about this so-called "September Effect" should shop around for a few evergreen growth stocks that are well-poised to flourish in future bear and bull markets.

I believe these three high-growth cloud stocks -- Workday (WDAY 1.42%), ServiceNow (NOW 0.06%), and Monday.com (MNDY 4.23%) -- are all still screaming buys as September starts. Let's find out a bit more about these three unstoppable growth stocks.

A couple counts cash at home.

Image source: Getty Images.

1. Workday

Workday's cloud-based human capital management (HCM) platform provides staffing, payroll, budgeting, and analytics tools. It currently serves more than 10,000 organizations globally, including over half of the Fortune 500. Its business model is well-insulated from economic downturns since its clients will still need to use its tools to lay off their staff, streamline their businesses, and optimize their spending.

Between fiscal 2018 and fiscal 2023 (which ended in January 2023), Workday grew its revenue at a compound annual growth rate (CAGR) of 24%. It expects its revenue to rise 18% in fiscal 2024, and during its latest conference call, co-CEO Carl Eschenbach said the company still hadn't "seen any pullback" caused by the current macro headwinds. Instead, Eschenbach declared that Workday's "value proposition is only resonating more" in this challenging environment as companies "consolidate" their HCM services to cut costs. That's probably why its net revenue retention rate remains above 100%.

Workday remained profitable by both generally accepted accounting principles (GAAP) and non-GAAP metrics throughout the first half of fiscal 2024. It trimmed 3% of its workforce earlier this year, but it still plans to expand its total headcount for the full year as it continues to invest in the expansion of its ecosystem. Analysts expect its non-GAAP EPS to grow 52% for the full year -- so its stock still doesn't seem too pricey at 44 times forward earnings.

2. ServiceNow

ServiceNow's cloud-based platform helps companies streamline their digital workflows, automate certain tasks, and increase their overall operating efficiency. It served more than 7,700 customers, including roughly 85% of the Fortune 500, at the end of 2022. Like Workday, ServiceNow is also naturally insulated from a lot of macro headwinds because its services help companies operate more efficiently through economic downturns.

From 2017 to 2022, ServiceNow grew its revenue at a CAGR of 31%. The tougher market drove some companies to rein in their software spending over the past year, but CEO Bill McDermott said it's still "set up very well for a strong second half" during its latest conference call. It also maintained a renewal rate of 99% in its latest quarter.

For 2023, it expects its subscription revenue, which accounts for most of its top line, to grow 25% in 2023 in constant currency terms. Unlike many other growing cloud companies, ServiceNow is consistently profitable by both GAAP and non-GAAP measures. Analysts expect its revenue and non-GAAP EPS to both grow about 23% for the full year.

But its longer-term outlook is even more impressive. It expects its annual revenue to exceed $16 billion in 2026, which implies it can still grow its top line at a CAGR of at least 21% from 2022 to 2026. Its stock might seem a bit pricey at 58 times forward earnings, but I believe its healthy long-term forecast easily justifies that higher valuation.

3. Monday.com

Monday.com's cloud-based platform enables companies to develop their own custom work management apps to accelerate or automate specific tasks. Its apps can either be built from scratch or created through pre-built "recipes" and then directly integrated into an organization's existing software infrastructure. It serves more than 186,000 companies worldwide -- most of which are small to medium-sized businesses.

Monday.com has grown rapidly since its IPO two years ago. Its revenue rose 91% in 2021 and 68% in 2022, and it expects 37% to 38% growth in 2023. That slowdown spooked some investors, but the secular expansion of the work management app market, the expansion of its AI platform (which assists in the development of AI-driven apps), and a warmer macro environment could all stabilize its near-term growth.

Monday.com wasn't profitable by non-GAAP measures in 2022, but it's expected to generate its first full-year non-GAAP profit this year. It's also been narrowing its GAAP losses, and its adjusted free cash flow (FCF) finally turned positive over the past year. Its net dollar retention rate among its larger customers, which generate more than $50,000 in annual recurring revenue, also remains comfortably above 100%.

Monday.com isn't a bargain at 175 times forward earnings and 12 times this year's sales, but it's a lot cheaper than it was at the apex of the growth stock rally in late 2021. Therefore, it could still become a potential multibagger from these levels.