decades ago, Cray Computers were assembled by people (housewives) who were allowed to spend no more time than they could be maximally effective in, using wires cut to millimeter-precise lengths.
Yes, and there's a Cray I at the Computer Museum here in Silicon Valley, upholstered base and all. You can sit on it if you like. It's not useful for much else.
All modern supercomputers are composed of a large number of microprocessors. The interconnects are faster than with ordinary hosting/cloud operations, but the CPUs are the same. The biggest supercomputer in the world, in China, is 3,120,000 cores of Intel Xeons, running at 2.2GHz each.
The question is whether the problem you're solving needs tight interconnection. If not, you can run it on a large number of ordinary computers. Weather may not be that tightly coupled; propagation time in air is kind of slow.