Pull growing-degree-day (GDD) data for turf pest/disease timing models via the ACIS Web Services API

Steps

1. Use the StnData call (data.rcc-acis.org/StnData) for a single station, or MultiStnData for several, specifying station identifier(s) and date range.
2. Request the 'gdd' element in your elems array, e.g. {"name":"gdd","interval":"dly","units":"degreeF","base":50} — adjust the base temperature to match the pest/disease model you're tracking (turf models commonly use base 50°F).
3. Submit simple browser-style GET calls for basic lookups, or POST a JSON 'params' object for more advanced multi-station/grid queries.
4. Use GridData instead of StnData/MultiStnData if you need a gridded GDD surface rather than point station values.
5. Parse 'M' as missing and 'T' as trace in returned values — these are ACIS's standard placeholder codes, not numeric zeros.
6. Cross-check turf-specific results against Cornell's Northeast Regional Climate Center base-50 GDD maps (nrcc.cornell.edu/industry/grass), which draw on the same underlying data.