7-5-1 that says...
7−5−1. AUTHORIZATION
a. SVFR operations in weather conditions less than basic VFR minima are authorized:
1. At any location not prohibited by 14 CFR Part 91, Appendix D or when an exemption to 14 CFR Part 91 has been granted and an associated LOA established. 14 CFR Part 91 does not prohibit SVFR helicopter operations.
2. Only within the lateral boundaries of Class B, Class C, Class D, or Class E surface areas, below 10,000 feet MSL.
3. Only when requested by the pilot.
4. On the basis of weather conditions reported at
the airport of intended landing/departure.
REFERENCE−
FAA Order JO 7110.65, Para 7−5−6, Climb to VFR.
FAA Order JO 7110.65, Para 7−5−7, Ground Visibility Below One Mile.
5. When weather conditions are not reported at the airport of intended landing/departure and the pilot advises that VFR cannot be maintained and requests SVFR.