Once you create a temp table, it is available to any code further down that procedure, and to any procedures that the initial procedure may call after the table has been created. So, this is the design you would be shooting for.

CREATE PROCEDURE SP_FillTable As

IF OBJECT_ID('tempdb..#AreaReadings') IS NULL CREATE TABLE #AreaReadings(col1 int)

INSERT INTO #AreaReadings

select ...

GO

CREATE PROCEDURE sp_CalculateResults AS

CREATE TABLE #AreaReadings (col1 int)

execute sp_FillTable

select * from #AreaReadings

GO

I'd be more worried about that

part.