に掛(か)けてOver (a period), From ~ until, Through

Coming from the る - Verb 掛(か)ける 'to suspend', にかけて conveys that something is happening 'over a period of time', 'from (A) until (B)', or 'all through (A)'. This grammar structure is a combination of the case marking particle に, and 掛(か)ける combined with the conjunction particle て. Literally, the meaning can be thought of as follows:

に - Marks (A) as the location/state.

掛(か)けて - States that something is 'suspended' (in an ongoing process) in that location/state.

The 'something' that is an ongoing process will usually be indicated by a (B) part of the sentence. This expression will primarily be used with nouns.

にかけて is primarily used in written language, although it appears quite often in the news as well, indicating that some weather pattern is expected to continue for a set period of time.

Caution

Occasionally, the adverbial particle は is used after にかけて. This transforms the meaning of 'all through (A)', to something similar to 'limited to within (A)'. Any (B) phrase in these types of sentences will be contrasting (B) with (A), rather than saying (B) is occurring within (A).

As we can see by these examples, this is an extension of the standard use of は, which shows that everything before it is a 'set state'. Therefore '(A) は (B)', means that 'only (A) defines (A), (B) is a separate entity/discussion'.