よく details

often + write

yoku kaku

often; a lot — or, of manner rather than count, well/thoroughly

meaning: write often

駅前えきまえの食堂しょくどうには、今いまでもよく行くいく。

ekimae no shokudou ni wa, ima demo yoku iku.

I still go often to the diner in front of the station. neutral

その気持きもち、よく分わかるよ。

sono kimochi, yoku wakaru yo.

I know exactly how you feel. casual

Examples

often; a lot — how many times something happens, with no upper bound implied

駅前えきまえの食堂しょくどうには、今いまでもよく行いく。

ekimae no shokudou ni wa, ima demo yoku iku.

I still go often to the diner in front of the station. neutral

あの人ひと、よく笑わらうよね。

ano hito, yoku warau yo ne.

That guy laughs a lot, doesn't he. casual

この辺へんは冬ふゆでもよく雨あめが降ふります。

kono hen wa fuyu demo yoku ame ga furimasu.

It rains a lot around here even in winter. neutral

well; thoroughly — the manner of the act rather than its frequency

その気持きもち、よく分わかるよ。

sono kimochi, yoku wakaru yo.

I know exactly how you feel. casual

ご利用りようの前まえに、説明書せつめいしょをよくお読よみください。

go riyou no mae ni, setsumeisho o yoku o yomi kudasai.

Please read the instructions carefully before use. formal

In the past the two senses collide: よく来きたね is praise for coming at
all, not a report that you came often.

時々
The same pre-verbal slot and the same job of counting occasions, but よく claims the act is the norm and says nothing about the gaps, while 時々 caps the count low and concedes the gaps are long — よく行いく advertises a habit, 時々行いく plays one down.
いつも
いつも is falsified by a single exception, よく is not — so よく遅おくれる complains about a tendency the speaker could still find counterexamples to, and いつも遅おくれる accuses the person of every occasion at once.

くなる
In よくなる the よく is なる's COMPLEMENT — the state reached, like 高たかくなる — not an adverb modifying it, so neither the "often" of よく行いく nor the "thoroughly" of よく分わかる is the right reading of 天気てんきがよくなる.